"  r 


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REPORT  ON  THE  ORGANIZATION  OF  THE  INTER- 
NATIONAL ASTRONOMICAL  UNION 

Presented  for  the  American  Section,  International  Astronomical  Union 
By  W.  W.  Campbell,  Chairman,  and  Joel  Stebbins,  Secretary 


A-<- 


-' — -^v-^' 


Published  in  the  Proceedings  of  the  National  Academy  of  Sciences, 
June,  1920,  vol.  6,  no.  6,  pages  349-396 


Announcement  Concerning  Publications 

of  the 
National  Research  Council 


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REPRINT  AND  CIRCULAR  SERIES 

OF  THE 

National  Research  Council 

NUMBER  10 


REPORT  ON  THE  ORGANIZATION  OF  THE   INTERNATIONAL 
,  ASTRONOMICAL  UNION  * 

Presented  for  the  American  Section,  International  Astronomical  Union 
By  W.  W.  Campbell,  Chairman,  and  Joel  vStebbins,  Secretary 

CONTENTS 

Report  of  the  Chairman  and  Secretary :?49 

Statutes  of  Convention 3.S.5 

International  Time  Commission 3.5'^ 

International  Central  Bureau  for  Astronomical  Telegrams 359 

Reports  of  Committees  of  the  American    Section  of   the  International  Astro- 
nomical Union 3^>o 

Report  of  the  Committee  on  Notation,  Units,  and  Economy  of  Publi- 
cation    360 

Report  of  the  Committee  on  Almanacs 363 

Report  of  the  Committee  on  Meridian  Astronomy 363 

Report  of  the  Committee  on  Cooperative  Work  with  the  vSpectrohelio- 

graph 365 

Report  of  the  Committee  on  EcHpses 366 

Report  of  the  Committee  on  Standards  of  Wave-length 367 

Report  of  the  Committee  on  the  Determination  of  Solar  Rotation  by 

the  Displacement  of  Lines 369 

Report  of  the  Committee  on  Wireless  Determination  of   Longitude.  .  .  .  372 

Report  of  the  Committee  on  Variation  of   I^atitude 373 

Report  of  the  Committee  on  Asteroids  and  Comets 374 

Report  of  the  Committee  on  Stellar  Parallaxes 380 

Report  of  the  Committee  on  Stellar  Photometry 381 

Report  of  the  Committee  on  Double  Stars 387 

Report  of  the  Committee  on  vStellar  Classification 391 

Report  of  the  Committee  on  Radial  Velocities 392 

Report  of  the  Committee  on  Reform  of  the  Calendar 393 

Report  of  the  Committee  on  Research  Surveys 395 

♦  Published  also  in  the  Proceedings  of  the  >!alioiiid  Aaulemy  of  Sciences,  6,  m2U  (349-396) 


INTERNATIONAL  ASTRONOMICAL   UNION  349 


REPORT  OF  THE  CHAIRMAN  AND  vSECRETARY 

The  American  delegation  to  the  conference  of  interalHed  academies 
held  in  London  in  October,  1918,  had  proposed  that  the  existing  organiza- 
tions relating  internationally  to  one  and  the  same  subject,  to  Astronomy 
for  example,  should  be  succeeded  by  a  single  society  so  formulated  as  to 
serve  the  purposes  of  all  the  associations  from  which  they  should  with- 
draw. This  policy  was  approved  by  the  conference.  At  meetings  held 
later  in  Paris  it  was  decided  that  representatives  of  Astronomy  in  the  al- 
lied and  associated  nations  should  meet  in  Brussels  in  July,  1919,  to  create 
the  International  Astronomical  Union. 

The  American  delegation  of  astronomers  was  organized  under  the  aus- 
pices of  the  National  Research  Council.  The  Council  proposed  that  the 
delegates  be  chosen  by  a  subsidiary  organization  known  as  the  American 
Section  of  the  (proposed)  Astronomical  Union ;  this  Section  for  the  present 
occasion  to  be  constituted  as  follows: 


National  Academy  of  Sciences — .5  members:  W.  W.  Campbell,  George  E-  Hale, 
A.  A.  MiCHELSON,  F.  R.  MouLTON,  Frank  Schlesinger. 

American  Astronomical  Society — 20  members:  C.  G.  Abbot,  W.  S.  Adams,  R.  G. 
AiTKEN,  S.  I.  Bailey,  E.  E.  Barnard,  L.  A.  Bauer,  Benjamin  Boss,  E.  W.  Brown, 
W.  S.  EiCHELBERGER,  E.  B.  Frost,  J.  F.  Hayford,  W.  J.  Humphreys,  W.  J.  Hussey, 
A.  O.  Leuschner,  S.  a.  Mitchell,  H.  N.  Russell,  C.  E.  St.  John,  F.  H.  Seares, 
V.  M.  Slipher,  Joel  Stebbins. 

American  Mathematical  Society — .3  members:  G.  D.  Birkhoff,  W.  D.  MacISIillan, 
R.  S.  Woodward. 

American  Physical  Society — 3  members:  J.  S.  Ames,  Henry  Crew,  Theodore 
Lyman. 

U.  S.  Coast  and  Geodetic  Survey — 1  member:     William  Bowie. 
U.  S.  Naval  Observatory — 1  member:     J.  A.  HooGEwERFF. 


The  members  selected  later  by  these  organizations  are  as  listed  above. 

The  American  Section  thus  constituted  held  its  first  meeting  in  the 
office  of  the  National  Research  Council,  Washington,  D.  C,  on  March 
8,  1919.  Twenty  of  the  thirty-three  members  were  present.  Mr.  W.  W. 
Campbell  was  appointed  permanent.  Chairman  of  the  Section,  and  Mr. 
Joel  Stebbins,  Secretary.  An  Executive  Committee  of  the  Section  was 
appointed,  consisting  of  the  Chairman,  the  Secretary,  and  Messrs.  C.  G. 
Abbot,  E.  W.  Brown,  and  Frank  Schlesinger.  The  Section  gave  assent 
to  the  acts  of  the  London  Conference,  and  formally  approved  the  proposal 
that  those  nations  which  had  remained  neutral  throughout  the  war  should 
be  admitted  into  the  International  Astronomical  Union  promptly  upon 


350  INTERNATIONAL  ASTRONOMICAL   UNION 

the  conclusion  of  peace.  The  Section  did  not  attempt  to  outhne  the  form 
of  an  international  organization  which  would  promise  the  greatest  use- 
fulness, but  concerned  itself  largely  with  the  technical  work  of  the  proposed 
Union  in  which  the  American  astronomers  would  be  chiefly  interested. 
The  Executive  Committee  was  instructed  to  appoint  subcommittees  of 
the  American  Section  which  should  prepare  reports  upon  nineteen  promi- 
nent divisions  of  astronomical  research,  for  presentation  at  a  later  meet- 
ing of  the  Section.  The  Brussels  delegation  was  selected  in  part,  and  the 
Executive  Committee  was  authorized  to  complete  it. 
The  delegation  was  eventually  composed  as  follows: 

W.  W.  Campbell,  Lick  Observatory,  Chairman;  W.  S.  Adams,  Mount  Wilson  Ob- 
servatory; Benjamin  Boss,  Dudley  Observatory,  Albany;  Major  Philip  Fox,  Dear- 
born Observatory,  Evanston,  at  that  time  with  the  American  Expeditionary  Forces 
in  France;  S.  A.  Mitchell,  McCormick  Observatory,  Virginia;  C.  E.  St.  John,  Mount 
Wilson  Observatory;  F.  H.  Seares,  Mount  Wilson  Observatory;  Frank  SchlEsinger, 
Allegheny  Observatory,  Pittsburgh;  JoEL  Stebbins,  University  of  Illinois,  Secretary. 

The  special  subcommittees  were  in  due  time  constituted,  as  follows: 

Committee  on  the  Variation  of  Latitude. — F.  B.  LiTTELL,  Chairman,  A.  O.  Leuschner, 
Frank  Schlesinger. 

It  was  voted  to  ask  the  American  Section  of  the  International  Geophysical  Union  to 
appoint  a  similar  committee  to  confer  and  make  a  joint  recommendation  on  the  most 
promising  method  of  continuing  the  variation  of  latitude  work. 

Committee  on  Standards  of  Wave-Length. — Henry  Crew,  Chairman,  H.  D.  Babcock, 
Keivin  Burns,  W.  W.  Campbell,  C.  E.  St.  John. 

Committee  on  Solar  Rotation. — C.  E-  St.  John,  Chairman,  W.  S.  Adams,  Frank 
Schlesinger. 

Committee  on  Eclipses. — S.  A.  Mitchell,  Chairman,  E.  E-  Barnard,  H.  D.  Curtis. 

Committee  on  Stellar  Classification. — H.  N.  RussELL,  Chairman,  W.  S.  Adams,  Miss 
Annie  J.  Cannon,  R.  H.  Curtiss. 

Committee  07i  Asteroids  and  Comets. — A.  O.  Leuschner,  Chairman,  E-  W.  Brown, 
G.  H.  Peters. 

Committee  on  Almanacs. — W.  S.  Eichelberger,  Chairman,  E.  W.  Brown,  R.  H. 
Tucker. 

Committee  on  Radial  Velocities. — -W.  W.  Campbell,  Chairman,  W.  S.  Adams,  J.  S. 
Plaskett. 

Committee  on  Double  Stars.— K.  G.  Aitken,    Chairman,  Eric  Doolittle,   W.   J. 

HUSSEY. 

Committee  on  Notation,  Units,  and  Economy  of  Publication. — W.  J.  Humphreys, 
Chairman,  E.  B.  Frost,  A.  O.  Leuschner. 

Committee  on  Meridian  Astronomy.— Bv;njamin  Boss,  Chairman,  F.  B.  Littell, 
Frank  Schlesinger. 

Committee  on  Abstracts  and  Bibliographies. — F.  E.  FowlE,  Chairman,  H.  D.  Curtis, 
G.  S.  Fulcher. 

Committee  on  Research  Surveys. — G.  E.  HalE,  Chairman,  F.  R.  Moulton,  Harlow 
Shapley. 

Committee  on  Stellar  Photometry. — F.  H.  SearES,  Chairman,  S.  I.  BailEY,  F.  C. 
Jordan,  J.  A.  Parkhurst,  Joel  Stebbins. 

Committee  on  Wireless  Determination  of  Longitude. — J.  A.  Hoogewerff,  Chairman, 
W.  W.  Campbell,  J.  J.  Carty.     This  committee  was  requested  to  study  the  feasibility 


INTERNATIONAL  ASTRONOMICAL   UNION  351 

of  determinations  of  longitude  by  wireless  at  widely  distributed  stations,  and  report 
on  what  seems  to  be  the  proper  time  and  method  for  such  undertakings. 

Committee  on  Solar  Radiation. — Mr.  C.  G.  Abbot  was  asked  to  prepare  a  report  on 
solar  radiation. 

Committee  on  the  Spectroheliograph . — The  Mount  Wilson  Observatory  was  asked  to 
prepare  a  report  on  work  with  the  spectroheliograph. 

Committee  on  Reform  of  the  Calendar. — R.  T.  Crawford,  Chairman,  W.  W.  Campbell, 
Harold  Jacoby. 

Another  subcommittee  was  appointed  at  a  later  date,  as  follows : 

Committee  on  Stellar  Parallaxes. — Frank  SchlESINGER,  Chairman,  W.  S.  Adams, 
S.  A.  Mitchell. 

The  American  Section  met  again  in  the  office  of  the  National  Research 
Council  on  June  23  and  24,  to  receive  and  act  upon  the  reports  of  the 
technical  subcommittees,  to  consider  questions  of  policy,  and  to  instruct 
the  delegation  which  would  represent  the  Section  at  Brussels.  Twenty 
members  of  the  Section  were  present.  The  reports  of  the  subcommittees, 
presenting  the  aspects  of  their  subjects  which  were  then  prominent  in  the 
minds  of  astronomers,  and  suggesting  promising  procedure  for  the  im- 
mediate future,  were  of  a  high  order  of  excellence.  They  are  appended 
to  this  report  in  the  form  in  which  they  were  adopted  by  the  Section. 
The  discussions,  conducted  with  enthusiasm  and  frankness,  were  extremely 
valuable. 

A  joint  meeting  of  the  American  Section  with  the  proposed  International 
Geodetic  and  Geophysical  Union  (Major  William  Bowie,  Chairman) 
was  held  on  June  24. 

The  delegation  of  astronomers  sailed  from  New  York  on  June  30  and 
reached  London  on  July  7.  The  next  ten  days  were  devoted  profitably 
and  with  unusual  pleasure  to  renewing  old  scientific  acquaintances  and 
making  many  new  ones,  to  learning  of  progress  in  astronomy  and  the  re- 
lated sciences  made  in  Great  Britain  during  the  war  period,  to  discussing 
with  our  British  colleagues  the  many  problems  coming  up  for  considera- 
tion at  the  Brussels  Conference,  etc. 

The  President  and  Council  of  the  Royal  Astronomical  Society  had  most 
kindly  arranged  by  cable  that  the  members  of  the  American  delegation 
should  attend  and  address  a  special  meeting  of  the  Society  on  the  after- 
noon of  July  11.  At  this  meeting,  under  the  presidency  of  Professor 
Fowler,  each  member  of  our  astronomical  delegation,  and  likewise  Dr. 
L.  A.  Bauer,  Secretary  of  the  Geophysical  Section,  addressed  the  Society 
informally  on  the  scientific  subject  which  at  that  time  especially  interested 
him.  This  meeting  had  been  preceded  by  a  reception  in  the  rooms  of  the 
Society,  which  gave  opportunity  to  meet  many  British  men  and  women 
whose  names  had  long  been  familiar. 

Opportunities  to  observe  the  equipment  and  work  of  the  Royal  Ob- 
servatory at  Greenwich,  of  the  University  observatories  at  Cambridge 
and  Oxford,  and  of  the  laboratory  of  Professor  Fowler  in  South  Kensington 
were  provided  by  members  of  their  staffs. 


352  INTERNATIONAL  ASTRONOMICAL   UNION 

In  common  with  many  British  colleagues,  the  American  delegation 
journeyed  from  London  to  Brussels  on  July  17.  The  Conference  lasted 
from  July  18  to  July  28,  inclusive.  Thirty-three  astronomical  delegates 
were  present:  eight  from  Belgium,  eight  from  Great  Britain,  seven  from 
France,  one  from  Italy,  and  nine  from  the  United  vStates. 

The  most  difficult  question  confronting  the  International  Astronomical 
Union  related  to  its  composition.  Should  it  be  organized  as  a  great  as- 
tronomical society,  comprehending  all  divisions  of  astronomical  science  in 
a  somewhat  general  or  indefinite  manner,  or  should  it  consist  of  working 
committees,  each  committee  concerned  with  some  definite  line  of  astro- 
nomical research?  Should  there,  for  example,  be  a  great  division  of  the 
Union  relating  to  the  solar  system,  or,  on  the  contrary,  several  compara- 
tively small  committees  occupying  themselves  responsibly  with  such  defi- 
nite subjects  as  solar  rotation,  eclipses,  solar  radiation,  etc.?  Should 
there  be  another  great  division  of  the  Union  relating  to  the  sidereal  sys- 
tem, or,  on  the  contrary,  several  comparatively  small  committees  occupying 
themselves  responsibly  with  such  definite  subjects  as  stellar  parallaxes, 
radial  velocities  of  the  stars,  double  stars,  variable  stars,  etc.?  The  latter 
plan  was  adopted.  To  begin  with,  thirty- two  such  special  committees  were 
established.  These  vary  in  size  in  accordance  with  the  requirements  and 
present  states  of  the  problems  concerned.  The  Committee  on  the  Carte 
du  Ciel  and  the  Committee  on  Meridian  Astronomy  are  relatively  large, 
with  more  than  a  dozen  members  each,  whereas  other  committees,  such 
as  those  on  Lunar  Nomenclature,  on  Solar  Radiation,  on  Astronomical 
Ephemerides,  etc.,  are  relatively  small,  with  not  more  than  half  a  dozen 
members  each.  The  separate  committees  are  working  bodies.  They  are 
intended  to  be  essentially  complete  in  themselves.  The  Union  as  a  whole 
will  meet  in  general  every  three  years  in  different  educational  centers  of 
the  world,  but  it  is  expected  that  the  members  of  a  given  committee  will 
find  many  occasions  between  general  meetings  when  conferences  by  letter 
or  otherwise  may  profitably  occur.  Committee  reports  will  doubtless 
aim  to  represent  the  views  of  the  committees  as  to  the  current  status  of 
their  subjects,  and  to  present  practical  suggestions  for  further  under- 
takings. In  other  words,  it  is  anticipated  that  each  committee  shall 
make  known  through  its  report,  presented  in  a  general  session  of  the  Union, 
those  aspects  of  its  subject  with  which  the  workers  in  that  subject  may 
most  profitably  acquaint  and  busy  themselves. 

Each  committee  has  power  to  add  to  its  numbers  by  favorable  vote  of 
two-thirds  of  the  current  membership  of  the  committee. 

It  is  provided  in  the  Constitution  that  the  committees  shall  automatically 
go  out  of  existence  at  the  close  of  each  triennial  meeting  of  the  Union. 
This  offers  the  opportunity  for  reorganization  upon  the  basis  of  those 
who  work. 

The  Constitution  of  the  Union,  as  distributed  from  the  office  of  the  Gen- 


INTERNATIONAL  ASTRONOMICAL   UNION  353 

eral  Secretary  of  the  International  Research  Council,  follows  this  report 
together  with  the  Regulations  of  the  International  Time  Commission  and 
of  the  International  Central  Bureau  for  Astronomical  Telegrams,  which 
were  adopted  by  the  Union. 

The  number  of  votes  and  the  relative  financial  obligations  of  each  ad- 
hering country  are  fixed  by  a  scale  identical  with  that  which  governs 
these  subjects  in  the  International  Research  Council.  The  unit  of  financial 
contribution  for  the  United  States  during  the  first  three  years  of  the  con- 
vention may  not  surpass  1,500  francs  annually.  In  this  connection  we 
should  note  the  fact  that,  upon  the  recommendation  of  the  American 
delegates  representing  Astronomy  and  Geophysics,  the  administration 
of  the  latitude  variation  problem  is  to  be  transferred  to  the  International 
Astronomical  Union.  The  financial  obligation  of  the  United  States  in 
support  of  this  work  is  one  of  the  larger  items  entering  into  the  financial 
budget  of  the  Astronomical  Union. 

The  budget  of  the  Astronomical  Union  for  subsequent  years  shall  be 
determined  in  a  manner  precisely  parallel  to  that  adopted  for  the  Re- 
search Council. 

The  following  officers  of  the  Astronomical  Union  were  elected  in  general 
session : 

President,  M.  Benjamin  Baillaud,  Director  of  the  Paris  Observatory. 

General  Secretary,  Alfred  Fowler,  F.R.S.,  Professor  of  Astrophysics,  Imperial 
College  of  Science  and  Technology,  South  Kensington,  London. 

Vice-Presidents,  W.  W.  Campbell,  Director  of  the  Lick  Observatory;  Sir  F.  W. 
Dyson,  the  Astronomer  Royal,  Greenwich,  London;  M.  Georges  Lecointe,  Director 
of  the  Royal  Observatory  of  Belgium,  Brussels;  M.  AnnibalE  Ricco,  Director  of  the 
Observatory  of  Mt.  Etna,  Sicily. 

The  fifth  vice-presidency  was  left  vacant  for  the  present,  pending  the 
adhesion  of  countries  which  had  remained  neutral  during  the  war.  The 
officers  here  listed  compose  the  Executive  Committee  of  the  Union. 

The  technical  committees  are  as  follows : 

L  Committee  on  Relativity. — Eddington,  Chairman,  Armellini,  Brillouin,  H.  D. 
Curtis,  De  Donder,  Ishiwara,  Jeans,  Levi-Civita,  E.  Picard. 

2.  Committee  on  the  Republication  of  Early  Astronomical  Works. — DreyER,  Chairman, 
Bigourdan,  BirkEnmayer,  Crew,  Knobel,  Mascart,  Terao. 

3.  Committee  on  Notation,  Units,  and  Economy  of  Publication. — Stroobant,  Chairman, 
Bigourdan,  Boss,  Deslandres,  Dyson,  Frost,  Turner. 

4.  Committee  on  Ephemerides. — CowELL,  Chairman,  Andoyer,  Brown,  Dyson, 
Eichelberger. 

5.  Committee  on  Abstracts  and  Bibliography. — Baillaud,  Chairman,  Bigourdan, 
H.  D.  Curtis,  Fowler,  Knobel,  Millosevich,  Stroobant. 

6.  Committee  on  Astronomical  Telegrams. — Lecointe,  Chairman,  BailEY,  Baillaud. 

7.  Committee  on  Dynamical  Astronomy  and  Astronomical  Tables. — Andoyer,  Chair- 
man, Brown,  Cowell,  Glaisher,  Hamy,  Leuschner,  Moulton,  Sampson. 

8.  Committee  on  Meridian  Astronomy  {including  Refraction). — Hough,  Chairman, 
Antoniazzi,  de  la  Baume  Pluvinel,  Bigourdan,  Boss,  Dyson,  Eddington,  Gon- 
nessiat,  Hamy,  Di  Legge,  Littell,  Philippot,  Porter,  Tucker,  (Australian). 


354  INTERNATIONAL  ASTRONOMICAL   UNION 

9.  Committee  on  Theoretical  and  Applied  Optics  and  the  Study  of  Instruments. — Hamy, 
Chairman,  Carty,  Conrady,  Cotton,  Delvosal,  Fabry,  Littell,  Lunn,  Sampson. 

10.  Committee  on  Solar  Radiation. — Abbot,  Chairman,  Bemporad,  Callendar, 
Deslandres,  Fowle,  Gorczynski. 

11.  Committee  on  the  Spectro-Helio-Enregislreur. — Deslandres,  Chairman. 

12.  Committee  on  the  Solar  Atmosphere. — HalE,  Chairman,  Deslandres,  Evershed, 
Fowler,  Hirayama,  Lee,  Newall,  Peirot,  Ricco,  St.  John. 

13.  Committee  on  Astronomical  Expeditions,  Eclipses,  etc. — de  LA  Baume  Pluvinel, 
Chairman,  Angot,  Barnard,  Campbell,  Deslandres,  Fowler,  Hinks,  Mitchell, 
Palazzo,  Ricc6. 

14.  Committee  on  the  Determination  of  Wave-Lengths  and  Tables  of  the  Solar  Spec- 
trum.— St.  John,  Chairman,  Babcock,  Fabry,  Fowler,  Hamy,  Meggers,  Merton, 
Nagaoka,  Newall,  Perot,  Wright. 

15.  Committee  on  Solar  Rotation. — Newall,  Chairman,  Adams,  Deslandres, 
Evershed,  DeLury,  Perot,  Sampson,  St.  John. 

16.  Committee  on  Physical  Observations  of  the  Planets. — Cerulli,  Chairman,  Barnard, 
Deslandres,  Jarry-Desloges,  Lampland,  Mascart,  Phillips,  Stroobant,  H. 
Thomson. 

17.  Committee  on  Lunar  Nomenclature. — Turner,  Chairman,  Bigourdan,  Miss 
Blagg,  Pickering,  Puiseux. 

18.  Committee  on  the  Determination  of  Terrestrial  Longitude  by  Wireless  Telegraphy. — 
General  Ferrie,  Chairman,  Bigourdan,  Carty,  Delporte,  Dyson,  Hamy,  Hooge- 
werff,  Hough,  Nakano,  Sampson. 

19.  Committee  on  the  Variation  of  Latitude. — Kimura,  Chairman,  DE  LA  Baume 
Pluvinel,  Bianchi,  Bigourdan,  Brillouin,  Celoria,  Hills,  Jeffreys,  Jones,  Lar- 
MOR,  Littell,  Reina,  Ross,  Schlesinger,  Volta. 

20.  Committee  on  Asteroids. — Brown,  Chairman,  Ant.  Abetti,  Andoyer,  Bigourdan, 
Bourget,  Cowell,  Crommelin,  Fayet,  Gonnessiat,  Krassowski,  Leuschner, 
Metcalf,  Millosevich,  Stroobant. 

21.  Committee  on  Comets. — LEuschner,  Chairman,  Andoyer,  de  la  Baume  Pluvinel, 
Barnard,  Crommelin,  Deslandres,  Fayet,  Fowler, 

22.  Committee  on  Meteors. — Denning,  Chairman,  Deslandres,  Lebeuf,  Mitchell, 
Olivier,  Mrs.  Wilson. 

23.  Committee  on  the  Carte  du  Ciel. — Turner,  Chairman,  Baillaud,  Balbi,  Baldwin, 
Bemporad,  Bhaskaran,  Cook,  Cosserat,  Curlewis,  Delvosal,  Dyson,  Gonnessiat, 
Hough,  Lecointe,  L.  Picart,  Ricco,  Sampson,  Schlesinger. 

24.  Committee  on  Stellar  Parallaxes. — Schlesinger,  Chairman,  G.  Abetti,  Adams, 
Bigourdan,  Cosserat,  Davidson,  Dyson,  Fox,  Miller,  Mitchell,  Rambaut, 
Van  Biesbroeck. 

25.  Committee  on  Stellar  Photometry. — Seares,  Chairman,  Baillaud,  Eddington, 
Halm,  Miss  Leavitt,  Melotte,  Parkhurst,  Sampson,  Turner. 

26.  Committee  on  Double  Stars. — Aitken,  Chairman,  G.  Abetti,  Bigourdan,  Doo- 
LiTTLE,  Espin,  Fox,  Hussey,  Jackson,  Jonckheere,  Van  Biesbroeck. 

27.  Committee  on  Variable  Stars. — Bailey,  Chairman,  Bemporad,  Brook,  Cosserat, 
Jordan,  Markwick,  Mascart,  Pace,  Phillips,  Plummer,  Russell,  Shapley,  Steb- 
bins.  Turner. 

28.  Committee  on  the  Nebulae. — Bigourdan,  Chairman,  Deslandres,  Dreyer, 
Fabry,  Knox-Shaw,  Newall,  Reynolds,  Slipher,  Wright. 

29.  Committee  on  the  Spectral  Classification  of  Stars.— Adams,  Chairman,  Miss  Can- 
non, R.  H.  CuRTiss,  Fowler,  de  Gramont,  Hamy,  Newall,  Plaskett,  Russell. 

30.  Committee  on  Stellar  Radial  Velocities. — Campbell,  Chairman,  Adams,  Deslan- 
dres, Hamy,  Lunt,  Newall,  Plaskett. 


INTERNATIONAL  ASTRONOMICAL   UNION  355 

31.  Committee  on  Time. — Sampson,  Chairman,  Baillaud,  Bigourdan,  Celoria, 
Dyson,  General  Ferrie,  Hoogewerff,  Hough,  Lecointe,  Philippot. 

32.  Committee  on  the  Reform  of  the  Calendar. — Cardinal  Mercier,  Honorary  Chair- 
man, Bigourdan,  Chairman,  Campbell,  Crawford,  Deslandres,  Dyson,  Lecointe, 
MiLLOSEvicH,  Ricco,  Sampson. 

Certain  of  the  committees,  such  as  those  on  Eclipses,  on  Time,  etc., 
held  meetings  in  Brussels  promptly  following  their  formation.  It  was 
deeply  regretted  that  the  work  of  organization  was  so  time-consuming  as 
to  prevent  nearly  all  of  the  committees  from  holding  first  meetings. 

The  invitation  of  the  Italian  delegates  that  the  next  meeting  of  the 
International  Astronomical  Union  should  be  held  in  Rome  in  the  year 
1922  was  accepted. 

The  earnestness  and  enthusiasm  with  which  the  work  of  organization 
was  conducted,  and  the  unanimity  with  which  decisions  were  finally  made, 
are  the  satisfactory  indications  that  the  Union  will  meet  efficiently  its 
purpose  of  promoting  astronomical  research  through  the  coordinated 
efforts  of  the  astronomers  in  many  countries. 
Respectfully  submitted, 

W.  W.  Campbell,  Chairman 
Joel  Stebbins,  Secretary 
American  Section,  International  Astronomical  Union. 

International  Research  Council 

INTERNATIONAL  ASTRONOMICAL  UNION 
Statutes  of  Convention 
I— Objects  of  the  Union  and  Conditions  of  Admission 
L     The  purpose  of  the  Union  is: 

(a)  To  faciUtate  the  relations  between  astronomers  of  different  countries  where 
international  cooperation  is  necessary  or  useful. 

(b)  To  promote  the  study  of  astronomy  in  all  its  departments. 

2.  The  admission  of  countries  to  the  Union  shall  be  subject  to  the  Regulations  of 
the  International  Research  Council. 

II — National  Committees 
•3.     A  National  Committee  shall  be  formed  in  each  of  the  countries  belonging  to  the 
Union.     It  shall  be  formed  under  the  responsibility  of  the  principal  Academy  of  the 
country  concerned,  or  of  its  National  Research  Council,  or  of  some  other  national 
institution  or  association  of  institutions,  or  of  its  Government. 

4.  The  functions  of  the  National  Committees  shall  be  to  promote  and  coordinate 
in  their  respective  countries  the  study  of  the  various  branches  of  Astronomy,  more 
especially  in  relation  to  their  international  requirements. 

They  shall  be  empowered  to  propose  singly  or  jointly  with  other  National  Committees 
questions  falling  within  the  purview  of  the  Union  for  discussion  by  the  Union. 

The  National  Committees  shall  nominate  delegates  to  represent  them  at  the  meetings 
of  the  Union. 

Ill — Administration  of  the  Union 

5.  The  work  of  the  Union  shall  be  directed  by  the  General  Assembly  of  the  delegates. 

6.  The  Bureau  of  the  Union  shall  consist  of  a  President,  not  more  than  five  Vice- 
Presidents,  and  a  General  Secretary,  who  shall  be  elected  by  the  General  Assembly, 


356  INTERNATIONAL  ASTRONOMICAL  UNION 

and  hold  office  until  the  end  of  the  second  General  Assembly  following  that  of  their 
election;  provided  that  the  first  President  and  three  of  the  first  Vice-Presidents  (as 
determined  by  the  drawing  of  lots)  shall  retire  at  the  end  of  the  first  General  Assembly 
following  that  of  their  election.     The  retiring  members  are  re-eligible. 

This  Bureau  shall  be  the  E.\ecutive  Committee  of  the  Union. 

The  five  Vice-Presidents  shall  be  chosen  so  as  to  represent  the  different  branches  of 
Astronomy. 

In  the  case  of  any  vacancj^  occurring  among  its  members,  the  Executive  Committee 
shall  have  power  to  fill  up  such  vacancy.  Any  person  so  appointed  shall  hold  office 
until  the  next  General  Assembly,  which  shall  then  proceed  to  an  election.  The  member 
thus  elected  shall  complete  the  term  of  office  of  the  person  whose  place  he  takes. 

There  shall  be  an  Administrative  Office,  which,  under  the  direction  of  the  General 
Secretary,  shall  conduct  the  correspondence,  preserve  the  archives,  prepare  and  issue 
the  publications  sanctioned  by  the  Union,  and  administer  its  funds. 

IV — Standing  Committees 

7.  The  General  Assembly  shall  appoint  Standing  Committees,  for  the  study  of  special 
branches  of  Astronomy,  the  encouragement  of  collective  investigations,  and  the  discus- 
sion of  questions  relating  to  international  agreements  or  to  standardization. 

The  Standing  Committees  shall  present  reports  of  their  work  to  the  Union. 

8.  The  President  and  the  members  of  each  Committee  are  elected  by  the  General 
Assembly  on  the  nomination  of  the  Executive  Committee  of  the  Union.  They  hold 
office  until  the  end  of  the  next  ordinary  General  Assembly,  and  are  re-eligible. 

When  a  Standing  Committee  is  composed  of  members  appointed  partly  by  the 
Astronomical  Union  and  partly  by  some  other  Union  connected  with  the  International 
Research  Council,  it  shall  have  the  power  to  elect  its  own  President. 

Standing  Committees  shall  draw  up  their  own  by-laws.  They  may  co-opt  other 
members  by  a  majority  of  two-thirds.  Such  co-opted  members  need  not  necessarily 
be  delegates,  but  shall  be  subjects  of  one  of  the  countries  adhering  to  the  Union. 

9.  With  the  sanction  of  the  Executive  Committee,  a  Standing  Committee  may 
issue  its  publications  independentlj'.  A  Standing  Committee  may  entrust  any  part 
of  its  work  to  any  national  institution  or  to  individuals. 

V — The  General  Assembly 

10.  The  General  Assembly  shall,  as  a  rule,  hold  an  ordinary  meeting  once  every 
three  years.  The  date  and  place  of  the  meeting,  unless  determined  by  the  General 
Assembly  at  its  previous  meeting,  shall  be  fixed  by  the  Executive  Committee,  and  com- 
municated at  least  four  months  beforehand  to  the  adhering  organizations. 

11.  For  special  reasons,  the  President  of  the  Union,  with  the  consent  of  the  Execu- 
tive Committee,  may  summon  an  extraordinary  meeting  of  the  General  Assembly. 
He  must  do  so  at  the  request  of  one-third  of  the  votes  of  the  countries  adhering  to  the 
Union. 

12.  All  members  of  the  National  Committees  may  attend  the  meetings  and  take 
part  in  the  discussions  of  the  General  Assembly  without  power  of  voting. 

The  President  of  the  Union  may  invite  scientific  men,  who  are  not  delegates,  to  at- 
tend a  meeting  of  the  General  Assembly,  provided  they  are  subjects  of  one  of  the  ad- 
hering countries.  Such  invited  guests  may  take  part  in  the  discussions,  but  shall  have 
no  power  of  voting. 

Members  of  any  committees  who  are  not  delegates  (Article  8)  shall  have  the  right  to 
attend  those  meetings  of  the  General  Assembly  which  deal  with  the  subjects  referred  to 
the  Committee. 

13.  The  agenda  of  business  to  be  transacted  at  a  meeting  shall  be  determined  by  the 
Executive  Committee  and  communicated  to  the  adhering  organizations  at  least  four 


INTERNATIONAL  ASTRONOMICAL   UNION  357 

months  before  the  first  day  of  the  meeting.  No  question  which  has  not  been  placed  on 
the  agenda  shall  be  discussed,  unless  a  proposal  to  that  effect  be  approved  by  one-half 
of  the  countries  represented  at  the  General  Assembly. 

VI — Finance  and  Voting  Power 

14.  The  Executive  Committee  shall  prepare  an  estimate  of  the  budget  for  each  of 
the  years  intervening  between  two  General  Assemblies.  A  Finance  Committee,  nomi- 
nated for  the  purpose  by  the  General  Assembly,  shall  examine  this  estimate  together 
with  the  accounts  for  the  preceding  years.  This  Committee  shall  submit  separate 
reports  on  the  two  questions  to  the  General  Assembly,  which,  having  considered  these 
reports,  shall  fix  the  unit  of  contribution  for  the  succeeding  period.  The  contributions 
due  from  the  adhering  countries,  and  their  corresponding  voting  powers,  are  determined 
by  the  population  of  the  country  according  to  the  following  scale: 


POPULATION 

NO.  OF  VOTES 

NO.   OF  UNITS  OF 
CONTRIBUTION 

Less  than  5  millions 

Between  5  and  10  millions 

Between  10  and  15  millions 

1 
2 
3 
4 
5 

1 

2 
3 

Between  15  and  20  millions 

5 

Over  20  millions 

8 

Each  country  is  at  liberty  to  include  in  its  population  the  inhabitants  of  its  colonies 
or  protectorates,  their  number  being  that  indicated  by  its  Government.  Self-govern- 
ing Dominions  (South  Africa,  Australia,  Canada,  New  Zealand)  have  separate  voting 
power  according  to  the  above  scale. 

The  contribution  to  be  levied  during  the  first  period  of  the  convention  shall  not 
exceed  1,500  francs  per  annum  per  unit.^ 

In  each  country  the  organization  adhering  to  the  Council  shall  be  responsible  for  the 
payment  of  the  contribution. 

15.  The  income  of  the  Union  is  to  be  dovoted  to: 

(a)  Cost  of  publication  and  expenses  of  administration. 

(b)  Cost  of  reduction  and  discussion  of  observations,  including  the  payment  of 
assistants. 

Funds  derived  from  donations  shall  be  used  by  the  Union,  in  accordance  with  the 
wishes  expressed  by  the  donors. 

If  any  country  withdraws  from  the  Union  it  resigns  at  the  same  time  its  rights  to  a 
share  in  the  assets  of  the  Union. 

16.  At  the  General  Assemblies  votes  upon  scientific  questions  shall  be  decided  by 
a  majority  of  votes  cast  by  the  delegates  present  and  voting.  In  questions  of  adminis- 
trative character,  and  all  questions  not  purely  scientific,  the  vote  shall  be  taken  by 
countries,  each  country  having  the  number  of  votes  designated  in  Article  14.  In  case 
of  doubt  as  to  the  category  to  which  a  question  belongs,  the  Chairman  of  the  meeting 
shall  decide.  Votes  taken  in  Committee  shall  be  counted  individually  and  not  by 
countries.  When  there  is  an  equal  division  of  votes,  the  Chairman  shall  in  all  cases 
have  a  second  or  casting  vote. 

17.  In  questions  of  an  administrative  character  which  appear  on  the  agenda  a  country 
not  represented  at  a  meeting  may  forward  its  vote  to  the  President  by  post,  and  such 
vote  shall  be  counted  if  received  before  the  vote  is  taken. 

>  The  value  of  the  franc  shall  be  that  of  the  French  currency. 


358  INTERNATIONAL  ASTRONOMICAL  UNION 

VII — Regulations 

18.  The  General  Assembly  may  draw  up  regulations  for  the  conduct  of  its  business, 
the  general  duties  to  be  assigned  to  the  officers  of  the  Union,  and  all  matters  not  provided 
for  in  the  Convention. 

Each  standing  Committee  may  draw  up  its  own  regulations,  which  shall  be  approved 
by  the  General  Assembly  before  coming  into  force. 

No  regulation  shall  be  made,  either  by  the  General  Assembly  or  by  the  Standing 
Committees,  which  violates  the  term  of  the  present  Convention. 

VIII — Duration  of  Convention  and  Modifications 

19.  The  present  Convention  shall  remain  in  force  until  December  31,  1931.  It 
may  then,  with  the  assent  of  adhering  countries,  be  continued  for  a  further  period  of 
twelve  years. 

20.  No  change  shall  be  made  in  the  terms  of  the  Convention  except  with  the  approval 
of  two-thirds  of  the  votes  of  the  adhering  countries. 

21.  The  French  te.\t  (of  which  the  above  is  a  translation)  shall  be  considered  to  be 
the  authoritative  text. 

International  Research  Council 

INTERNATIONAL  ASTRONOMICAL  UNION 

International  Time  Commission 

Regulations 

1.  An  International  Time  Commission  shall  be  formed  for  the  purpose  of  unifying 
time  by  means  of  radio-telegraphic  or  other  signals,  whether  these  are  scientific  signals 
of  great  precision,  or  ordinary  signals  adapted  to  the  needs  of  navigation,  meteorology, 
seismology,  railways,  postal  and  telegraphic  services,  public  administration,  clock- 
makers,  individuals,  etc. 

2.  The  domicile  of  the  Commission  shall  be  located  at  Paris. 

3.  The  Bureau  shall  consist  of  a  President,  a  Vice-President,  and  a  General  Secre- 
tary; the  latter  two  shall  be  elected  by  the  Commission  itself.  The  General  Secretary, 
whose  tenure  of  office  shall  terminate  on  December  31,  1931,  shall  fulfil  the  functions 
of  Director  of  the  International  Time  Bureau. 

4.  The  purpose  of  the  International  Time  Bureau,  located  at  the  National  Observa- 
tory of  Paris,  is : 

(a)  As  regards  ordinary  signals,  to  harmonize  the  determinations  of  universal  time, 
expressed  in  Greenwich  Time,  which  shall  be  transmitted  to  them  by  the  National 
Time  centers.  These  shall  be  responsible  for  calculating,  with  the  highest  obtainable 
precision,  the  mean  time,  as  deduced  from  determinations  made  by  the  Observatories 
of  their  respective  countries.  These  results  shall  be  sent  as  quickly  as  possible  to 
the  emitting  stations  and  to  the  National  Centers. 

{b)  As  regards  scientific  signals  of  precision,  to  harmonize  the  time  determinations 
made  by  the  associated  observatories,  and  deduce  from  them  the  most  exact  time. 

The  International  Time  Bureau  shall  publish  the  results  of  its  comparisons.  Any 
result  whose  publication  is  delayed  shall  be  communicated  in  detail  to  all  scientific 
associations  and  official  institutions  which  may  send  in  a  request  to  that  effect. 

5.  In  addition  to  the  Director,  the  International  Time  Bureau  shall  consist  of: 
(a)  Scientific  collaborators,  nominated  and  dismissed  by  the  Commission,  on  the 

proposal  of  the  Director  of  the  International  Bureau.  They  shall  be  charged,  with 
or  without  indemnification,  with  the  conduct  of  special  studies.  Their  term  of  office 
shall  not  exceed  two  years,  but  they  shall  be  re-eligible. 


INTERNATIONAL  ASTRONOMICAL   UNION  359 

(b)  Scientific  assistants,  nominated  and  dismissed  by  the  Director  of  the  International 
Bureau.  They  shall  be  responsible  for  the  carrying  out  of  the  programme  drawn  up 
by  the  Commission.  Their  term  of  office  shall  not  exceed  four  years,  but  they  shall 
be  re-eligible. 

The  budget  shall  determine  the  sums  allocated  to  each  of  these  classes. 

6.  The  Director  of  the  International  Bureau  shall  publish  the  results  of  the  work 
undertaken  in  accordance  with  the  decisions  of  the  Commission.  He  shall  present  to 
the  President  an  annual  report  covering  the  whole  field  of  activity  of  the  Bureau, 
together  with  the  programme  of  work  for  the  following  year.  This  report  and  pro- 
gramme shall  be  published. 

In  his  capacity  of  General  Secretary,  he  shall,  in  consultation  with  the  President,  con- 
duct the  correspondence  and  administer  the  funds.  He  shall  be  responsible  for  the 
custody  of  documents. 

7.  The  Director  of  the  International  Bureau  shall  prepare  the  estimate  for  the 
budget,  which,  after  having  been  approved  by  the  President  and  the  Commission, 
shall  be  submitted  to  the  International  Astronomical  Union. 

8.  The  income  of  the  Commission  shall  be  devoted  to: 

(a)  Covering  the  expenses  of  administration  and  publication. 

(b)  Honorarium  to  the  General  Secretary  as  Director  of  the  International  Time 
Bureau. 

(c)  Grants  or  remunerations  for  calculations,  observations,  or  experiments  under- 
taken at  the  request  of  the  Commission. 

(d)  The  purchase  and  upkeep  of  material  for  the  International  Time  Bureau. 

The  Director  of  the  Bureau,  under  the  control  of  the  International  Astronomical  Union, 
shall  be  responsible  for  the  expenditure  allocated  to  the  above  objects. 

9.  The  above  regulations  shall  remain  in  force  until  December  31 ,  1931. 

International  Research  Council 
INTERNATIONAL  ASTRONOMICAL  UNION 

International  Central  Bureau  for  Astronomical  Telegrams 
Regulations 

1.  The  purpose  of  the  Central  Bureau  is  to  receive,  centralize,  and  dispatch  informa- 
tion concerning  astronomical  discoveries,  observations,  and  calculations,  either  by 
telegram  or  by  post  to  the  various  institutions  or  private  persons  subscribing  to  it. 

2.  The  domicile  of  the  Bureau  shall  be  located  at  the  Royal  Observatory  of  Belgium, 
at  Uccle;  the  Chief  of  this  Institution  shall  act  as  its  Director. 

3.  The  Bureau  shall  be  placed  under  the  control  of  the  vStanding  Committee  on 
Astronomical  Telegrams. 

4.  Observatories  and  similar  institutions  may  subscribe  at  the  Central  Bureau  for 
Astronomical  Telegrams.  The  general  expenses  of  the  Central  Bureau  shall  be  divided 
equally  between  the  subscribers.  At  the  beginning  of  each  year  the  Standing  Committee 
on  the  proposal  of  the  Director,  shall  fix  the  annual  subscription,  which  shall  not  ex- 
ceed 25  francs  (French  currency),  payable  in  advance.  These  funds  shall  be  used  ex- 
clusively for  the  expenses  of  printing  the  circulars  and  the  correspondence.  In  addi- 
tion to  his  subscription  each  subscriber  shall  cover  the  expenses  of  all  telegrams  addressed 
to  him. 

0.     A  statement  of  all  expenses  shall  be  made  at  the  end  of  each  year. 

6.  Subscribers  shall  give  priority  to  the  Central  Bureau  in  respect  of  information 
on  their  discoveries,  observations,  or  important  calculations.  Expenses  incurred  in  the 
dispatch  of  telegrams  for  this  purpose  shall  be  refunded  to  the  senders. 


36o  INTERNATIONAL  ASTRONOMICAL   UNION 

7.  The  Central  Bureau  shall  take  the  necessary  measures  to  reach  its  subscribers 
in  all  parts  of  the  world.  If  necessary,  special  agreements  shall  be  made  for  this  purpose 
with  observatories  or  secondary  centers  situated  in  other  continents  which  may  serve 
as  relays. 

8.  The  Central  Bureau  shall  make  every  effort  to  reduce  the  expenses  of  transmission 
to  a  minimum;  it  shall  continue  to  employ,  for  this  purpose,  the  numeric  code  that  has 
been  in  use  for  several  years. 

Notes 

A.  Telegrams  sent  to  the  Central  Bureau  are  to  be  addressed: 

Astra  Bruxelles 

B.  Subscribers  are  requested  to  inform  the  Director  of  the  Royal  Observatory  of 
Belgium,  Uccle,  of  the  shortest  telegraphic  address  to  which  messages  conveying 
notices  of  discoveries  should  be  sent  in  order  to  reach  them. 

Reports  of  Committees  of  the  American  Section  of  the 
International  Astronomical  Union 

REPORT  OF  THE  COAJMITTEE  ON  NOTATION,  UNITS,  AND 
ECONOMY  OP  PUBLICATION 

The  Committee  on  Notation,  Units,  and  Economy  of  Publication  has 
given  careful  consideration  to  these  subjects,  and,  although  it  has  no 
recommendations  it  wishes  to  urge  upon  the  Union,  it  begs  to  submit 
the  following  remarks  in  support  of  the  appointment  of  a  similar  inter- 
national committee. 

I.      UNITS 

The  multiplicity  of  units,  applying  to  the  same  kind  of  measurement, 
that  are  now  used  in  astronomical  literature,  and  the  indefiniteness  that 
attaches  to  some  of  them,  suggest  the  need  of  a  careful  study  of  this  sub- 
ject and  international  agreement  as  to  what  units  should,  as  a  rule,  be 
adopted. 

Astronomical  distances,  for  instance,  are  already  expressed  in  terms 
of  the  kilometer,  mile,  "astronomical  unit"  (mean  solar  distance),  light- 
year,  "parsec"  (distance  corresponding  to  a  parallax  of  1"),  siriometer 
(corresponding  to  a  parallax  of  0."2),  "the  unit"  (corresponding  to  a  paral- 
lax of  0."1),  megaparsec  =   10"  parsecs,  and,  perhaps,  a  few  other  units. 

Although  no  other  astronomical  quantity  is  measured  in  so  many  differ- 
ent units  as  the  stellar  distance  there  are  some  whose  numerical  values  are 
more  confusing  because  the  name  of  the  unit  employed  has  at  least  a  double 
meaning.  Thus  the  "absolute  magnittide"  of  a  star  may  refer  to  its  bright- 
ness in  terms  of  some  supposed  constant;  or  to  that  brightness  which  the 
star  under  discussion  would  show  at  a  distance  of  10  parsecs.  Similarly, 
the  unit  of  heat  commonly  used  in  certain  astronomical  discussions,  the 
calorie,  often  leaves  one  in  doubt  as  to  which  calorie  is  meant,  the  small 
or  the  large. 


INTERNATIONAL  ASTRONOMICAL   UNION  361 

Ob\dously,  then,  there  is  need  for  general  agreement  in  respect  to  the 
units  to  be  used. 

The  following  suggestions  are  offered  for  discussion : 

1.  Distance. — So  far  as  practicable  let  the  unit  distance  be,  a,  the  kilo- 
meter (in  reference  to  dimensions  of  sun,  planets,  etc.).  It  can  even  be  used 
in  expressing  stellar  distances  without  employing  larger  numbers  than  the 
chemist  and  the  physicist  are  accustomed  to  in  speaking  of  the  number  of 
molecules  in  a  cubic  centimeter  of  gas),  b,  the  "astronomical  unit"  (in 
reference  to  the  solar  system  chiefly),  c,  the  light-year  (especially  in  popular 
articles),  and  d,  the  parsec  (wherever  appropriate),  or  preferably  a  unit 
10  times  as  great,  to  be  given  a  separate  name. 

2.  Absolute  magnitude. — The  meaning  given  to  the  expression  "absolute 
magnitude"  should  be  the  magnitude  at  the  distance  of  10  parsecs,  at  which 
the  star's  parallax  would  be  0."10. 

3.  Unit  of  heat. — Use  the  joule  for  the  unit  of  heat  instead  of  calorie, 
as  the  latter  is  not  definite  unless  explained. 

4.  Unit  of  wave-length. — Use  the  international  angstrom. 

5.  Unit  of  pressure. — One  bar  =  10^  dynes  per  square  centimeter. 
This  is  in  keeping  with  very  general  use  in  meteorology. 

II.      NOTATION 

It  is  only  right  that  considerable  latitude  should  be  allowed  the  author 
in  the  choice  of  notation,  nevertheless  some  of  the  existing  confusion  could 
and  should  be  avoided.  There  is  no  uniformity,  for  instance,  in  the  nota- 
tion for  the  elements  of  a  visual  binary  system.  Also  different  methods 
are  used  in  designating  the  brighter  stars — by  constellations  and  Greek 
letters,  and  by  right  ascension  and  declination.  Again,  the  notation  used 
in  celestial  mechanics,  though  difficult  to  standardize,  appears  to  be  more 
confused  than  necessary. 

Suggestions 

1.  Binary  systems. — Use  a  common  notation — Aitken's,  perhaps. 

2.  System  of  units. — If  metric  units  are  used  do  not  add  the  English 
equivalents;  if  English  units  are  used  add,  generally,  the  metric  equivalents. 

3.  Wave-length  system. — Use  the  abbreviations  /  5  and  R  S,  and 
not  /  A  and  R  A.  Do  not  use  the  diacritical  mark  over  either  the  ab- 
breviation A  or  the  word  angstrom. 

4.  Unit  of  acceleration. — A  short  name  is  needed  for  the  C.  G.  S.  unit  of 
acceleration. 

Additional  suggestions  in  reference  to  notation  will  be  made  in  connec- 
tion with  "economy  of  publication." 

Ill       ECONOMY   OF   PUBLICATION 

That  there  is  need  for  economy  in  amount  of  publication,  in  cost  of  pub- 
lication, and  in  manner  of  publication  so  as  to  save  the  time  and  effort 


362 


INTERNATIONAL  ASTRONOMICAL  UNION 


of  the  reader,  are  all  too  evident  to  admit  of  question.     The  problem  is 
how  can  these  results  be  best  attained. 

Suggestions 

1.  Observatory  bulletins. — There  should  be  as  few  bulletins  and  as  little 
published  in  them  as  circumstances  will  permit.  It  is  better  to  publish 
in  standard  journals  and  purchase  reprints. 

2.  References. — A  nearer  approach  to  standardization  of  references  to 
journals,  etc.,  than  now  exists  should  be  adopted — librarian's  method 
perhaps. 

3.  Standard  kinds  of  work. — So  far  as  practicable  all  results  obtained  in 
any  one  standard  line  of  work  should  be  presented  in  the  same  form. 

4.  Summaries. — Most  articles  should  end  with  concise  and  accurate 
summaries. 

5.  Catalogues. — -Catalogues  of  scientific  literature  should  give  concise 
abstracts. 

6.  Economy  in  typesetting. — Manuscript  should  be  kept  as  free  as  prac- 
ticable from  all  letters,  symbols,  and  combinations  that  worry  the  printer 
or  annoy  the  reader.  Greek  letters,  for  instance,  are  expensive  luxuries 
- — a  dime  per  letter  being  the  estimated  added  cost  of  publication.  Simi- 
larly, subscripts,  superscripts,  inferior  bars,  superior  bars,  vertical  frac- 
tions, etc.,  should  be  avoided  as  far  as  practicable. 

The  following  recent  suggestions  by  the  London  Mathematical  Society 
are  excellent: 


Instead  of 

V2,  ^,  Vis 

V2 


V; 


Always  print 

V2  or  2^^  1/V2  or  2~'^  Vl3  or 
13'^ 

V(a,v-2  -f  2bx  +  c)  or  {ax^  +  2bx 
+  c)'^ 

yJ{a/b)  or  (a/b)  ^ 


V— 1 


n.n  -[-1.71-1-2 

(|«)2,  \n  -f-  1,  \2n,  2"|n 

X,  y,  r,  e 
aa-\-ba-]rb-\-c 


n{n  -f  l)(u  -H  2) 

(«!)2,  («  +  1)!,  (2;0!,  2".7z! 

x' ,  y',  r',  B"  (by  preference) 

{a,  {{a  -\-  b),\{a  -\-  b  +  c) 


a  +  b       a 
c       b  -^  c  b 


{a  +  b)/c,  a/{b  -f  c),  a/b  -h  c 


INTERNATIONAL  ASTRONOMICAL  UNION  363 

-,  -  +  -  p/q,  p/q  +  r/s  (in  current  text) 

q    q        s 


^-  or  pl  (q  +  -)  p/{q  +  r/s) 

-  r/s  \         s/ 

\/xOV%-\   1/x"  OTX-" 


q  +  r,s 

1     1 

~>  ~ 

X    X 

2         X  P  -\-  2^  ^ 

r    ,    s         .    z  \r  -\-\s      y  -{-  z/t 

-  +  -    y  +  - 
3       4  t 

_nTrx       _  *2_  -mvx/l    ^- x^/4kt 

g      I  ^  e    4kt  e  ,e 

Itt 


a  J  0  J  0  J  0      J  0 

(2/7)    I     sin  {rirx/l)  sin  (57rx//)dT  -    I 

»/  0  ^  ^  0 


■/n 


2    z''     .     rTT.Y    .     sirx   ,  , 
sm  —  sin  —  ax 
I  I 


A  few  of  the  above  expressions  might,  perhaps,  be  written  in  still  better 
forms.  Furthermore,  it  is  quite  possible  to  write  an  integral  with  limits 
in  a  more  condensed  and  more  convenient  form  than  it  usually  has.     Thus 

Instead  of  Write 

xMx  J*[a,b]xHx 


/: 


b 

The  first,  or  usual,  form  occupies,  vertically,    the    space    of    two    lines. 
The  proposed  form  occupies  but  one  line. 

W.  J.  Humphreys,  Chairman,  Edwin  B.  Frost,  A.  O.  Leuschner. 

REPORT  OF  THE  COMMITTEE  ON  ALMANACS 

The  Committee  on  Almanacs  recommends  to  the  American  Section 
that  its  delegates  to  the  Brussels  meeting  of  July  18,  1919,  be  instructed 
to  endeavor  to  secure  the  adoption  by  the  International  Astronomical 
Union,  of  the  Report  of  the  Committee  on  Beginning  the  Day  at  Mid- 
night adopted  by  the  American  Astronomical  Society  in  August  1918. 
W.  S.  EiCHELBERGER,  Chairman,  E.  W.  Brown,  R.  H.  Tucker 

REPORT  OF  THE  COMMITTEE  ON  MERIDIAN  ASTRONOMY 

The  experience  gained  through  the  application  of  photography  to  the 
determining  of   stellar  positions   demonstrates   that  it    is  advantageous 

*  It  may  be  noted  that  an  integral  with  limits  always  involves  a  double  line;  so  that 
the  ordinary  notation  for  fractions  involves  no  additional  use  of  "spaces"  beyond  those 
required  for  the  integral  in  any  case. 


364  INTERNATIONAL  ASTRONOMICAL  UNION 

to  secure  star  positions,  as  far  as  possible,  by  photographic  methods.  This 
leads  to  the  suggestion  of  the  following  meridian  program,  which  is  de- 
signed to  provide  the  necessary  foundation  for  photographic  astrometry. 
The  suggested  plan,  in  brief,  is  to  adopt  3000  fundamental  stars  as  the 
initial  basis  of  the  system,  to  build  about  40,000  reference  stars  upon  this 
and  then  by  photographic  means  to  continue  a  list  of  reference  stars  to 
fainter  magnitudes.     The  details  of  the  plan  follow. 

I.      STANDARD   STARS 

It  is  suggested  that  the  list  of  fundamental  stars  compiled  in  1910  by 
the  Committee  on  Fundamental  Stars  of  the  Astrographic  Chart,  and  pub- 
lished in  the  supplement  to  the  Connaissance  des  Temps  for  1914,  be 
adopted. 

II.   PHOTOGRAPHIC  REFERENCE  STARS 

As  a  secondary  step  toward  providing  a  suitable  structure  upon  which 
to  base  photographic  plate  determinations  of  stellar  positions  it  is  suggested 
that  a  list  of  stars  be  constructed,  approximately  one  in  each  square  de- 
gree, and  included  as  far  as  possible  between  visual  magnitudes  8.0  and  9.0. 
The  list  should  favor  the  stars  of  the  intermediary  and  reference  lists  of 
the  Astrographic  Chart,  but  in  any  event  stars  which  have  been  previously 
observed  should  be  selected. 

III.      DIFFERENTIAL   MERIDIAN    OBSERVATIONS 

It  is  recommended  that  differential  observations  be  undertaken  in  zones 
20°  wide,  four  observations  being  taken  of  each  star,  two  in  each  position 
of  the  clamp.  All  the  fundamental  stars  in  each  zone  should  be  observed, 
together  with  a  sufficient  number  of  fundamental  stars  at  varying  decli- 
nations to  link  the  zone  with  the  fundamental  system. 

IV.      REVISION    OF   STANDARD    SYSTEMS 

Because  of  the  rapidity  with  which  the  weight  of  a  star  position  di- 
minishes, it  is  recommended  that  standard  systems  be  revised  every  fifteen 
to  twenty  years,  and  that  the  results  be  incorporated  in  the  ephemerides 
as  they  become  available. 

v.      QUESTIONNAIRE 

In  order  to  disseminate  information  in  compact  form  among  the  meridian 
observers,  it  is  recommended  that  6  months  before  each  meeting  of  the 
International  Astronomical  Union  the  following  questionnaire  be  sent  to 
each  observatory  and  that  the  reports  be  collated  and  published  as  part 
of  the  proceedings  of  the  meeting. 

1.  Brief  description  of  meridian  work  in  hand,  and  estimated  time  of  conclusion. 

2.  Instruments,  character,  size,  etc. 

3.  Equipment: 


INTERNATIONAL  ASTRONOMICAL   UNION  365 

(a)   Collimators 

{b)  Mires 

(c)  Nadirs 

{d)  Impersonal  right-ascension  micrometers 

(e)  Personal  equation  apparatus 

(/)  Reversing  prism  on  ocular — on  microscopes 

(g)  Screens  or  other  devices  for  magnitude 

(h)  Flexure — how  determined 

{i)  Clock — how  safeguarded  from  temperature  and  barometric  changes 

(j)  Thermometer  installation — use  of  whirling  thermometers — Assman  thermometers 

— or  other  devices 
{k)  Printing  chronograph 

(/)     Devices  for  stabilizing  mercury  reflecting  surfaces 
{m)  Methods  of  determining  corrections  for  irregularities  in  the  forms  of  the  pivots 

4.  Remarks  on  any  novel  devices  in  use,  with  comments  on  the  value  of  the  same. 

5.  Reflected  observations  of  stars.     Are  they  made — how  used? 

6.  Application  of  photography  to  meridian  work. 

7.  Method  of  determining  graduation  errors. 

VI.      PUBLICATIONS 

1.  The  present  practice  varies  from  publication  of  the  minute  detail 
of  observations  to  that  of  giving  only  the  final  results.  It  is  suggested  that 
this  matter  be  considered  and  that  a  recommendation  be  made  in  order 
on  the  one  hand  to  save  the  great  waste  of  material  and  effort  involved  in 
unnecessarily  extended  publication  and  on  the  other  hand  to  secure  the 
publication  of  as  much  detail  as  the  consensus  of  opinion  shall  decide  is 
actually  desirable. 

2.  Uniformity  should  be  observed  in  star  names,  in  number  of  decimals 
for  right-ascension  and  declination,  and  in  use  of  declinations  instead  of 
north  polar  distances. 

3.  Standard  equinoxes  should  be  adopted. 

4.  No  proper  motions  should  be  applied  in  observational  catalogues  to 
reduce  from  the  epoch  of  observation  to  the  date  of  equinox  of  the  cata- 
logue. 

VII.      SOUTHERN    OBSERVATORIES 

Attention  is  called  to  the  need  of  more  southern  observatories  for  meridian 
w^ork  in  view  of  the  relative  weakness  of  the  positions  of  the  southern  stars. 
Benjamin  Boss,  Chairman,  Frank  Schlesinger,  Frank  B.  Littell 

REPORT  OF  THE  COMMITTEE  ON  COOPERATIVE  WORK 
WITH  THE  SPECTROHELIOGRAPH 

In  several  reports  presented  to  the  International  Union  for  Cooperation 
in  Solar  Research,  the  advantages  of  photographing  the  sun  frequently 
with  the  spectroheliograph  at  several  stations  widely  separated  in  longi- 
tude have  been  pointed  out.  Without  enumerating  these,  it  is  evident 
that  a  more  nearly  continuous  record  of  the  rapidly  changing  phenomena 
of  the  sun's  atmosphere  than  we  now  possess  would  provide  material  for 


366  INTERNATIONAL  ASTRONOMICAL  UNION 

the  study  of  many  questions,  such  as  the  possible  connection  between  solar 
eruptions  and  terrestrial  magnetic  storms. 

Most  of  the  telescopes  hitherto  used  for  this  work  give  a  very  small 
solar  image,  while  the  spectroheliographs  employed  with  them  are  in  very 
few  cases  of  sufficient  dispersion  to  permit  satisfactory  photographs  to  be 
taken  with  the  Ha  line  As  the  hydrogen  flocculi,  for  most  purposes,  are 
of  much  greater  interest  and  importance  than  the  calcium  flocculi,  the 
object  of  this  report  is  to  indicate  the  general  nature  of  the  instrumental 
equipment  needed  to  record  them  in  such  a  way  as  to  render  the  resulting 
photographs  fairly  comparable. 

The  chief  instrumental  requirements  are: 

1.  A  telescope  giving  a  large  solar  image,  not  less  than  10  cm.  and  pref- 
erably from  15  to  20  cm.  in  diameter.  This  large  scale  is  needed  in  order 
that  the  minute  structure  defining  the  fields  of  force  of  the  hydrogen  flocculi 
may  be  clearly  recorded. 

2.  A  spectroheliograph  of  sufficient  dispersion  to  permit  the  hydrogen 
flocculi  to  be  photographed  with  light  confined  to  the  central  part  of 
the  Ha  line.     A  linear  dispersion  of  1  mm.  =  3.5  A  will  serve  very  well. 

It  is  desirable,  but  not  essential,  that  this  spectroheliograph  should  be 
of  sufficient  aperture  to  permit  the  entire  solar  image  to  be  photographed 
at  once.  If  this  is  not  feasible,  a  second  objective,  giving  a  smaller  solar 
image  (at  least  5  cm.  in  diameter),  should  be  so  attached  to  the  telescope 
that  it  can  be  readily  substituted  for  the  objective  of  greater  focal  length. 

3.  It  is  important  that  spectroheliograms  intended  for  comparative 
studies  of  eruptive  phenomena  and  changes  in  the  structure  of  the  hydrogen 
flocculi  should  not  differ  greatly,  either  in  the  size  of  the  solar  image  or 
in  the  dispersion  of  the  spectroheliographs  with  which  they  are  taken. 
For  this  reason  it  is  desirable  that  the  optical  constants  of  the  instruments 
used  at  cooperating  observatories  should  be  as  nearly  alike  as  possible. 

4.  It  is  desirable  that  the  spectroheliographs  should  be  adaptable  for 
the  photography  of  the  calcium  flocculi  with  K2  and  with  K3.  It  would 
also  be  advantageous  to  design  them  for  use  as  spectroregistreurs  des 
vitesses  (Deslandres)  and  for  the  study  of  the  magnetic  fields  in  sun-spots, 
in  case  spectrographs  especially  designed  for  these  purposes  are  not  avail- 
able. 

A  final  word  should  be  said  regarding  the  necessity  for  good  atmospheric 
conditions,  to  permit  the  sun  to  be  photographed  on  the  largest  possible 
number  of  days  and  to  afiford  the  perfection  of  definition  required  to  reveal 
the  minute  details  of  the  flocculi. 

George;  E.  Hale. 

REPORT  OF  THE  COMMITTEE  ON  ECLIPSES 
(Abstract) 
The  Committee  believes  that  it  might  be  of  assistance  to  astronomy 
along  the  following  lines: 


INTERNATIONAL  ASTRONOMICAL  UNION  367 

1.  To  advise  as  to  what  eclipse  problems  are  most  worthy  of  attack, 
and  what  equipment  is  needed  for  successful  work. 

2.  For  the  eclipse  of  1923,  to  collect  well  in  advance  all  available  in- 
formation regarding'  possible  eclipse  sites,  weather  probabilities,  trans- 
portation facilities,  living  conditions,  etc.  (The  Mexican  Meteorological 
Service  has  already  been  communicated  with  in  regard  to  the  eclipse  of 

1923.) 

3.  To  publish  such  information  and  eclipse  computations  well  in  ad- 
vance. 

4.  To  advise  intending  observers  as  to  location  so  as  to  secure  a  wide 
distribution  of  stations. 

5.  To  gain  information  regarding  the  apparatus  that  is  available  at 
different  observatories,  and  to  arrange  as  a  central  clearing-house  for  the 
loan  of  apparatus  to  intending  observers  who  have  not  adequate  facilities. 

A  discussion  is  given  of  the  various  eclipse  problems  under  the  headings : 
Photography  of  the  corona. 

What  is  the  corona? 

What  causes  the  corona? 

Motion  of  the  corona. 
Polarized  light  in  the  corona. 
Brightness  of  the  corona. 
Spectrum  of  the  corona. 

Wave-lengths  of  coronal  lines  and  rotation  of  the  corona. 
Flash  spectrum. 
Einstein  effect. 
Times  of  contact. 
Other  eclipse  problems. 
Movie  camera. 

S.  A.  Mitchell,  Chairman,  E.  E.  Barnard,  H.  D.  Curtis. 

REPORT  OF  THE  COMMITTEE  ON  STANDARDS   OF  WAVE-LENGTH 

1.  It  is  recommended  that  the  International  Astronomical  Union 
appoint  at  the  earliest  practicable  date,  a  committee  whose  functions  shall 
be  essentially  the  same  as  those  of  the  Committee  on  Wave-Lengths  of 
the  International  Union  for  Cooperation  in  Solar  Research. 

2.  The  primary  standard. — The  remarkable  sharpness  of  the  red  Cad- 
mium line,  the  extraordinary  skill  with  which  the  meter  was  evaluated  in 
terms  of  this  wave-length,  and  the  final  definition  of  the  angstrom,  as  an 
arbitrary  unit,  by  the  international  Solar  Union  at  Paris  in  1907,  would 
seem  to  place  the  primary  standard  almost  beyond  the  range  of  question. 

However,  the  recent  perfection  of  a  new  method  for  making  end-stand- 
ards of  length,  the  comparative  ease  with  which  the  optical  length  of  these 
end-standards  can  be  determined,  and  the  possible  superiority  of  some  other 


368  INTERNATIONAL  ASTRONOMICAL  UNION 

line  (such  as  the  bright  yellow  Neon  line)  over  one  from  solid  Cadmium 
as  a  source  of  light  combine  to  urge  a  reconsideration  even  of  the  primary- 
standard. 

Since  a  committee,  consisting  of  Messrs.  Ames,  Anderson,  Michelson 
and  Stratton,  has  been  appointed  by  the  National  Research  Council  to 
consider  the  practicability  of  adopting  a  wave-length  of  light  as  the 
fundamental  standard  of  length,  it  is  recommended  that  the  question 
of  a  primary  standard  of  wave-length  be  held  in  abeyance — that  is,  not 
reopened — until  the  above-mentioned  committee  makes  its  report. 

In  case  the  International  Bureau  of  Weights  and  Measures  adopts  a 
certain  wave-length  of  light  as  their  standard  of  length,  it  would  appear 
to  follow,  as  a  matter  of  course,  that  this  wave-length  should  be  adopted 
also  by  the  Astronomical  Union,  and  that  the  numerical  value  attached 
to  it  should  be  that  assigned  by  the  International  Bureau  of  Weights  and 
Measures. 

As  to  the  possible  use  of  a  Neon  line,  or  the  sharp  component  of  the 
green  Merciu^y  line,  or  of  a  sharp  line  in  the  absorption  spectrum  of  Iodine, 
for  the  fundamental  unit  of  length,  instead  of  the  red  Cadmium  line, 
your  committee  feels  that  this  is  a  matter  belonging  entirely  to  the  Com- 
mittee of  the  International  Bureau  of  Weights  and  Measures. 

3.  Secondary  standards. — A  series  of  secondary  standards  is  now  being 
determined  at  the  Bureau  of  Standards  and  at  Mt.  Wilson.  The  Committee 
recommends  that  the  Astronomical  Union  encourage  a  third  series  of  inde- 
pendent measures  on  these  lines. 

It  is  recommended,  therefore,  that  the  International  Astronomical  Union 
arrange,  if  possible,  with  European  spectroscopists  for  a  determination  of 
these  secondary  standards  in  Iron,  Neon,  and  other  substances  which  can 
be  worked  under  definite  and  easily  reproducible  conditions. 

The  dearth  of  Secondary  Standards  in  the  yellow-green  region  and  in 
the  infra-red  appears  to  your  committee  an  unsolved  problem.  Its  solu- 
tion will  be  the  discovery  of  a  workable  and  easily  duplicated  source  of  light 
which  will  furnish  properly  distributed  lines  of  sufficient  sharpness  and  in- 
tensity. 

4.  Tertiary  standards. — Here  the  greatest  need  appears  to  be  for  lines 
to  fill  gaps  in  the  ultra-violet,  the  yellow-green,  and  infra-red  of  Iron. 
With  reference  to  this  need  your  committee  has  no  recommendation  to 
make  except  to  seek  further  information  as  to  how  the  need  may  be  met. 

For  the  measurement  of  tertiary  standards  independent  determinations 
by  the  interferometer  and  by  the  grating  are  urgently  recommended,  on 
the  ground  that  the  errors  of  these  two  instruments  are  largely  comple- 
mentary. The  importance  of  this  work  is  emphasized  by  the  fact  that 
it  will  be  scarcely  practicable  to  print  a  new  "Table  of  Stronger  Lines" 
for  the  identification  of  impurities  and  similar  purposes  until  the  tertiary 
standards  are  more  complete  than  at  present. 


INTERNATIONAL  ASTRONOMICAL  UNION  369 

5.  Sources. — In  order  to  obtain  lines  of  constant  wave-length  and  con- 
stant intensity-distribution,  it  is  recommended  that  the  modification  of 
the  Pfund  arc  employed  at  Mt.  Wilson  be  adopted,  namely,  the  Pfund 
arc  operated  between  110  and  250  volts  as  convenient,  with  5  amperes  or 
less,  at  a  length  of  12  millimeters,  and  used  over  a  central  zone,  at  right 
angles  to  the  axis  of  the  arc,  not  to  exceed  IV4  millimeters  in  width. 

6.  Classification. — It  is  recommended  that  tables  of  wave-lengths  be 
accompanied  by  at  least  two  descriptive  columns,  one  indicating  the  in- 
herent nature  of  the  line  (intensity,  sharpness,  asymmetry,  etc.),  the  other 
indicating  the  character  of  the  measures  on  the  line.  There  is  urgent  need 
of  some  quantitative  description  of  relative  intensity  as  a  function  of  wave- 
length. 

For  indicating  the  intrinsic  character  of  the  line,  the  modification  of 
Gale  and  Adams'  groups,  shortly  to  be  defined  at  Mt.  Wilson,  is  recom- 
mended. 

For  indicating  the  degree  of  accuracy,  the  notation  of  Burns  {Lick 
Obs.  Bulletin  No.  247,  p.  29  and  Bulletin  Bureau  oj  Standards,  No.  274, 
p.  251)  is  recommended. 

7.  Tables  of  wave-lengths. — The  time  for  an  accurate  and  definitive 
determination  of  the  wave-lengths  of  the  different  chemical  elements  does 
not  yet  seem  to  have  arrived. 

It  is  recommended,  however,  that  a  Table  of  Stronger  Lines  in  which  wave- 
lengths of  all  elements  shall  be  arranged  in  order  of  magnitude  be  prepared 
at  the  earliest  practicable  date.  It  is  believed  that  present  needs  call 
for  a  table  containing  approximately  twice  as  many  lines  as  Kayser's 
Tabelle  der  Hauptlinien,  which  includes  ten  thousand  wave-lengths  and 
occupies  one  hundred  octavo  pages. 

8.  Survey. — It  is  recommended  that  the  conference  at  Brussels  consider 
the  possibility  and  advisability  of  making  a  survey  of  facilities,  equipment, 
and  opportunities  for  spectroscopic  work  in  the  various  laboratories  of 
the  world,  looking  toward  the  avoidance  of  unnecessary  duplication  and 
the  encouragement  of  cooperation  in  research. 

Henry  Crew,  Chairman,  Harold  D.  Babcock,  Keivin  Burns,  W.  W. 
Campbell,  Charles  E.  St.  John. 

REPORT  OF  THE  COMMITTEE  ON  THE  DETERMINATION  OF  SOLAR 
ROTATION  BY  THE  DISPLACEMENT  OF  LINES 

Since  the  Bonn  meeting  of  the  International  Union  for  Cooperation  in 
Solar  Research  in  1913,  results  of  investigations  of  the  sun's  rotation  have 
been  published  by  a  number  of  observers,  namely,  J.  S.  Plaskett,  Hubrecht, 
Schlesinger,  DeLury,  Evershed  and  Royds,  H.  H.  Plaskett,  and  St.  John 
and  Ware. 

As  the  data  relative  to  the  linear  velocity  at  the  solar  equator  now  cover 


370 


INTERNATIONAL  ASTRONOMICAL   UNION 


a  period  of  some  twenty  years,  a  review  of  the  results  at  this  time  is  of 
interest : 

Linear  Velocity  of  Solar  Rotation  at  the  Equator 


Duner 

Halm 

Adams 

Adams 

Storey  and  Wilson . .  . 

Plaskett,  J.  S 

Plaskett,  J.  S 

DeLury 

Hubrecht 

Plaskett,  J.  S 

Schlesinger 

Evershed  and  Royds. 

Plaskett,  H.  H 

St.  John  and  Ware.  . 

Plaskett,  H.  H 

St.  John  and  Ware.  . 
St.  John  and  Ware.  . 


VELOCITY 

NO.  OF  LINES 

REGION 

DATE 

2.08 

2 

6301-6302 

1900-5 

2.04 

2 

6301-6302 

1904 

2.06 

20 

4196-4294 

1907 

2.05 

22 

4196-4291 

1908.5 

2.08 

10 

6280-6318 

1909 

2.01 

19 

5506-5688 

1911 

2.02 

15 

4196-4291 

1911 

1.97 

19 

5506-5688 

1911 

1.86 

40 

4299-4400 

1911 

2.01 

27 

4250-5600 

1911-12- 

-13 

2.00 

20 

4058-4276 

1912 

1.95 

3906-5624 

1913 

1.98 

12 

5574-5628 

1913 

1,94 

35 

4123-4338 

1914 

1.95 

5 

5900 

1915 

1.94 

26 

5018-5316 

1914-18 

1.95 

7 

6265-6337 

1916-17 

In  view  of  the  accuracy  attainable  in  spectro-photographic  measures  the 
differences  between  these  results  are  surprising  and  disappointing  and  are 
the  outstanding  feature  in  the  problem  of  solar  rotation.  They  are  larger 
than  the  probable  errors  of  measurement,  and  either  depend  upon  sys- 
tematic errors  of  the  measurers  or  they  are  of  solar  or  terrestrial  origin. 
The  tracing  of  them  to  their  source  is  the  line  along  which  investigation 
may  be  directed  with  great  advantage. 

Investigations  now  in  progress  at  Mount  Wilson,  in  which  simultaneous 
observations  are  made  upon  the  two  limbs  and  the  center  of  the  sun, 
indicate  that  temporary  and  local  conditions  in  the  sun's  reversing  layer  are 
frequently  such  as  to  produce  differences  of  ten  per  cent  in  the  rotation 
values  obtained  by  comparing  east  and  west  limbs  directly. 

The  observations  show  further  that  high  values  at  one  limb  are  not 
correlated  with  high  values  at  the  other  as  they  would  be  if  they  were  due 
to  real  changes  in  the  rotation  of  the  reversing  layer  or  to  conditions  in 
the  terrestrial  atmosphere.  In  the  light  of  these  results  it  is  clear  that  a 
short  series  of  observations  may  give  misleading  results  and  it  even  be- 
comes a  question  whether  the  solar  rotation  can  be  determined  as  defi- 
nitely as  has  been  thought.  The  means  of  extended  series  of  observations 
taken  under  constant  conditions  should,  however,  give  results  of  great 
value.  Such  a  series  at  Mount  Wilson  Observatory  is  now  in  its  sixth 
year.  The  observations  show  no  definite  evidence  of  periodicity  in  the 
suns'  rotation  from  1914  to  1919,  but  furnish  strong  indications  of  fre- 


INTERNATIONAL  ASTRONOMICAL   UNION 


371 


quent  local  disturbances  of  a  definite  type  in  the  sun's  reversing  layer,  a 
subject  still  under  investigation. 

The  formulae  of  Faye  represent  satisfactorily  the  relation  of  velocity 
to  latitude  as  given  by  the  observations  of  Duner,  Adams,  Plaskett  and 
DeLury,  and  Schlesinger,  but  observ^ations  in  the  higher  latitudes  should 
be  greatly  extended  both  in  number  and  in  range  of  latitude.  The  failure 
of  the  Faye  formula  to  represent  Hubrecht's  observations  is  probably  due 
to  the  very  limited  time  covered  by  them. 

The  only  published  results  relating  to  a  difference  in  the  rotation  law 
in  the  two  hemispheres  are  those  of  Hubrecht.  His  earlier  paper  (1912) 
referred  to  in  the  report  at  the  Bonn  meeting  showed  an  excess  of  the  ve- 
locities in  the  southern  over  the  northern  hemispheres,  but  in  the  later 
publication  (1915)  covering  the  same  epoch  he  comes  to  the  opposite  re- 
sult basing  his  conclusions  upon  Tunstall's  measurement  of  his  plates  to 
the  exclusion  of  his  own.  The  question  of  a  difference  between  the  two 
hemispheres  is  one  of  great  interest  and  need  not  wait  for  solution  until 
all  discrepancies  between  observers  are  settled  as  it  is  a  relative  matter 
for  any  one  observer  and  instrument.  It,  therefore,  offers  an  inviting 
field  of  investigation  at  the  present  time,  and  is  on  the  working  program 
at  Mount  Wilson. 

The  different  rates  of  rotation  for  different  levels  in  the  solar  atmos- 
phere shown  by  the  Mount  Wilson  observations  of  Adams  appear  again 
in  preliminary  reductions  of  the  present  Mount  Wilson  series  which  show 
relatively  high  velocities  for  the  strong  magnesium  triplet  in  the  green, 
for  4227  and  the  H  and  A'  lines  of  calcium,  but  low  values  for  the  lines  of 
lanthanum  and  of  the  nitrogen  (cyanogen)  band  at  3883.  The  observa- 
tions of  Schlesinger  published  since  the  Bonn  meeting  agree  with  those  of 
Plaskett  and  DeLury,  vStorey  and  Wilson,  and  Hubrecht  in  showing  no 
positive  evidence  of  differences  in  rotational  velocity  It  is  to  be  noted 
that  in  the  Mount  Wilson  observations  lines  differing  widely  in  intensity, 
representing  great  differences  in  level,  have  been  employed.  As  differ- 
ences in  rotational  velocity  must  be  directly  related  to  differences  in  level, 
such  lines,  notwithstanding  the  difficulties  of  measurement,  offer  a  valuable 
means  of  detecting  it.  The  great  majority  of  lines  of  medium  intensity 
of  the  common  elements  originate  in  not  greatly  different  levels,  and  for 
such  lines  differences  in  rotation  and  velocity  would  be  small  and  corre- 
spondingly difficult  to  detect. 

Conditions  in  the  earth's  atmosphere  have  been  suggested  by  DeLury 
as  possible  causes  of  divergent  results  in  observations  for  solar  rotation. 
He  finds  evidence  of  the  effect  of  an  over-lapping  sky  spectrum  in  some  of 
his  observations  at  Ottawa,  and  attributed  to  it  the  large  variations  in 
rotational  velocity  at  different  times  and  all  differences  found  for  different 
elements  and  lines. 

That  a  large  proportion  of  superposed  skylight  might  appreciably  re- 


372  INTERNATIONAL  ASTRONOMICAL   UNION 

duce  line  displacements  at  the  sun's  limb  has  been  taken  into  considera- 
tion by  all  solar  observers.  Tests  on  Mount  Wilson  show  that,  under 
ordinary  observing  conditions,  the  integrated  light  just  outside  the  solar 
image  is  not  of  sufficient  intensity  to  affect  the  photographic  plate  during 
the  exposure  time  employed  for  solar  rotation  plates;  that  it  requires  con- 
siderable cloudiness  over  and  around  the  sun,  conditions  never  approxi- 
mated in  regular  work,  to  cause  a  measureable  decrease  in  the  line  dis- 
placements at  the  limb;  and  that  this  large  proportion  of  superposed  sky- 
light produces  no  differential  effects  between  strong  and  weak  lines. 

Recommendations  for  Program  of  Work 

1.  In  order  to  trace  to  their  source  the  systematic  differences  that 
are  found  in  the  value  of  the  solar  rotation  by  different  observers,  it  is 
desirable  that  further  study  be  given  to  possible  sources  of  systematic 
errors  and  to  determining  the  source  of  the  differences  found  by  the  same 
observer  upon  plates  taken  at  frequent  intervals,  differences  of  the  same 
order  of  magnitude  as  those  between  different  observers. 

2.  In  the  meantime  it  is  desirable  to  carry  on,  when  possible,  continuous 
series  of  observations  under  constant  instrumental  conditions  and  by 
the  same  observer. 

3.  As  it  seems  increasingly  probable  that  local  conditions  in  the  re- 
versing layer  are  frequent  causes  of  divergent  results,  it  is  advisable  to 
extend  observations  over  a  considerable  period  of  time  in  investigation 
of  such  questions  as  variation  with  latitude  or  differences  between  the 
hemispheres. 

4.  Simultaneous  observation  on  the  center  and  the  limb  is  recommended 
as  a  valuable  means  of  checking  results  and  of  investigating  the  hemi- 
spheres separately. 

We  recommend  the  appointment  of  an  International  Committee  on 
Solar  Rotation  determined  by  spectrographic  methods,  the  four  points 
above  to  be  referred  as  suggestions  to  this  committee. 

C.  E.  St.  John,  Chairman,  W.  S.  Adams,  Frank  vSchlesinger. 

REPORT  OF  THE  COMMITTEE  ON  WIRELESS  DETERMINATION 

OF  LONGITUDE 

The  Committee  recommends : 

1.  That  the  American  delegation  to  the  Brussels  meeting  of  the  Inter- 
national Astronomical  Union  urge  the  desirability  of  a  Division  of  the 
Union  which  shall  promote  in  the  most  practicable  manner  a  world-wide 
program  of  accurate  radio  determinations  of  differences  of  longitudes, 
on  the  basis  of  one  general  program  to  be  supported  by  the  inter-allied 
nations  concerned. 

2.  That  the  American  members  of  this  Division  or  Committee  of  the 
Union  should  be  selected  by  the  American  Delegation  with  reference 


INTERNATIONAL  ASTRONOMICAL   UNION  373 

to  their  fitness  for  planning,  directing,   and  carrying  on  the  American 
Section  of  the  inter-alHed  program. 

3.  That  the  selected  primary  stations  be  so  distributed  throughout 
both  the  southern  and  northern  hemispheres  as  to  cover,  as  uniformly  as 
possible,  the  entire  world,  and  to  give  suitable  checks  on  the  work. 

4.  That  observatories  and  other  related  institutions,  both  govern- 
ment and  private,  be  encouraged  to  participate  by  receiving  the  funda- 
mental radio  signals  and  making  simultaneous  time  observations,  so  as 
to  link  up  as  many  positions  as  possible  with  the  primary  stations. 

5.  That  the  governments  controlling  radio  stations  likely  to  be  of  use 
be  asked  to  give  their  consent  to  and  promises  of  assistance  in  the  work. 

6.  That  Greenwich,  England,  be  so  included  in  the  plans  that  the 
differences  of  longitude  between  it  and  the  primary  stations  will  be  ac- 
curately determined. 

7.  That  the  determination  of  the  difference  of  longitude  between 
any  pair  or  pairs  of  primary  stations  be  made  by  parties  from  one  country 
which  would  select  their  instruments  and  work  out  and  be  responsible 
for  the  result;  but  that  nothing  in  this  recommendation  would  prevent 
a  duplication  of  this  work  by  observers  from  another  country,  and,  where 
other  checks  were  not  provided,  that  such  duplication  be  encouraged. 

8.  That  in  view  of  the  many  arrangements  and  preparations  required 
to  secure  accurate  and  complete  results,  the  earliest  date  practicable  for 
an  international  determination  of  differences  of  longitudes  is  the  winter 
of  1921-22. 

J.  A.  HooGEwERFF,  Chairman,  W.  W.  Campbell. 
Because  of  his  absence,  Mr.  J.  J.  Carty  did  not  see  the  report. 

REPORT  OF  THE  COMMITTEE  ON  VARIATION  OF  LATITUDE 

The  Committee  on  Variation  of  Latitude  of  the  American  Section  of 
the  proposed  International  Astronomical  Union  submits  the  following 
report,  based  upon  the  action  taken  at  a  joint  meeting  of  this  committee 
with  a  similar  committee  representing  the  American  Section  of  the  pro- 
posed International  Geophysical  Union  held  in  Washington  on  April 
29,  1919.  There  were  present  at  the  meeting  Messrs.  Bowie  and  Marvin 
representing  the  Geophysical  Union  and  Messrs.  Schlesinger,  Leuschner, 
and  Littell  representing  the  Astronomical  Union.  Mr.  Bowie  acted  as 
chairman  and  Mr.  Littell  as  secretary  of  the  meeting. 

RECOMMENDATIONS 

The  following  recommendations  are  made  by  the  committee: 

1.     That  the  observations  for  variation  of  latitude,  their  reduction, 

and   their   publication   be   entrusted   to   the  International  Astronomical 

Union. 


374  INTERNATIONAL  ASTRONOMICAL  UNION 

2.  That  the  continuity  of  the  observations  by  the  present  methods 
at  the  four  international  variation  of  latitude  stations,  Ukiah,  California; 
Carloforte,  Italy;  Mizusawa,  Japan;  and  Charjui,  Turkestan  be  main- 
tained, as  far  as  practicable,  and  that  the  matter  of  utilizing  the  obser\^a- 
tions  made  at  other  stations  be  considered. 

3.  That  the  question  of  renewing  variation  of  latitude  observations 
in  the  southern  hemisphere  be  considered. 

4.  That,  inasmuch  as  no  definite  plan  can  be  advanced  for  defraying 
the  expense  of  the  variation  of  latitude  work  until  some  international 
arrangement  is  formulated,  the  several  nations  maintain  the  stations 
within  their  domains,  and  that  some  provisional  arrangement  be  made 
for  caring  for  the  records,  reductions,  and  publications,  pending  a  perma- 
nent organization  of  the  work. 

Frank  B.  Littell,  Chairman,  A.  O.  Leuschner,  Frank  SchlEsinger 

REPORT  OF  THE  COMMITTEE  ON  AvSTEROIDvS  AND  COMETS 

Among  the  most  important  objects  to  be  served  by  the  discovery, 
observ^ations,  and  by  researches  in  general  on  comets  and  asteroids,  are 
the  following : 

1.  Testing  of  gravitation  by  comparison  of  theory  and  observation 
leading  to  deviation  from  the  law  (e.g.,  those  shown  by  the  moon). 

2.  Testing  of  gravitational  theories  as  sufficient  to  represent  their 
motions  for  some  time  in  the  past  and  future. 

3.  Distribution  with  reference  to  theories  of  formation  and  evolution. 

4.  Distribution  of  orbits  with  reference  to  theories  of  the  stability  of 
their  motions. 

5.  Positions  for  photometric  research. 

6.  Photometric  research  for  testing  of  theories  of  causes  of  variation 
of  light. 

7.  Theories  of  distribution  tested  by  search  for  asteroids  in  regions 
indicated  by  theory. 

8.  Positions  of  asteroids  recorded  for  future  researches,  the  direction 
of  which  is  at  present  unknown. 

These  ultimate  aims  involve: 

Observations  of  position,  visual  and  photographic; 

Photometric  observations,  visual  and  photographic; 

Methods  of  observation  and  reduction ; 

Researches  in  orbit  methods  and  orbit  determinations,  preliminary 
and  final,  and  ephemerides; 

Methods  of  special  and  general  perturbations,  of  varying  degree  of 
accuracy  according  to  special  requirements; 

Researches  in  pure  celestial  mechanics  (e.g.,  periodic  solutions),  etc.,  etc. 

Complete  bibliographies  should  be  prepared  for  each  line  of  work. 


INTERNATIONAL  ASTRONOMICAL   UNION  375 

The  Committee  is  of  the  opinion  that  much  unnecessary  effort  and 
duphcation  could  be  avoided  and  a  thorough  foundation  for  future  re- 
searches along  the  lines  indicated  above  could  be  furnished  by  first  of  all 
bringing  together  all  published  material  in  a  bibliography  which  would 
give  in  abstract  form  the  results  of  past  observations  and  investigations. 
Observations  of  positions,  photometric  observations,  etc.,  would  be  listed 
merely  by  dates  of  observation  and  references.  At  the  present  time  there 
is  completely  lacking  a  reference  work  for  asteroids  such  as  Galle's  Comet 
List.  The  latter  also  requires  to  be  brought  up  to  date;  several  fragmen- 
tary continuations  of  Galle's  list  are  in  existence.  Bauschinger's  Sta- 
tistik  der  Kleinen  Planeten  gives  merely  statistical  information  based  on 
adopted  asteroid  orbits,  without  giving  a  complete  history  of  the  work 
done  on  the  individual  asteroids,  including  references  to  the  dates  of  ob- 
servations. 

The  research  requirements  along  the  various  lines  indicated  above  can- 
not be  fully  stated  until  a  complete  history  and  bibliography  for  comets 
and  asteroids  are  available.  Galle's  list  has  been  of  incomparable  value 
in  this  direction,  particularly  in  the  identification  of  comets.  After  the 
history  and  bibliography  have  been  completed  the  research  requirements 
along  the  various  lines  indicated  above  should  be  published. 

Arrangements  should  be  made  by  international  cooperation  for  the  pub- 
lication of  opposition  ephemerides. 

After  the  plans  have  been  outlined  in  the  rough  and  published,  a  census 
should  be  made  of  observatories  and  astronomers,  for  the  purpose  of 
securing  volunteers  for  specific  work  of  observation  or  research.  The 
results  of  this  census  should  be  published,  so  that  every  astronomer  will 
know  to  whom  to  turn  for  information  of  any  kind  regarding  asteroids, 
and  so  as  to  avoid  the  present  useless  duplications,  particularly  of  observa- 
tion. 

The  general  direction  of  these  plans  should  be  in  charge  of  an  international 
committee  composed  of  the  chairmen  of  the  Committees  on  Comets  and 
Asteroids  of  the  various  national  sections. 

As  a  first  step  toward  the  realization  of  the  foregoing  plans  it  is  neces- 
sary to  adopt  a  distinct  classification  for  comets  and  asteroids.  An 
example  for  a  suitable  asteroid  classification  is  attached  as  Appendix  A. 
This  classification  is  based  on  the  present  state  of  observation  and  com- 
putation and  on  the  scientific  importance  of  the  object.  It  at  once  en- 
ables the  astronomer  interested  in  a  particular  kind  of  research  to  select 
the  object  and  the  material  needed. 

The  present  designation  of  asteroids  might  be  supplemented  by  using 
the  letters  a,  b,  c,  etc.,  for  easy  recognition  of  the  condition  of  the  avail- 
able observational  material  and  of  its  orbit  theory,  an  asterisk  being  added 
to  designate  those  of  scientific  importance.  These  asteroids  might  be 
given  a  description  to  indicate  the  nature  of  their  scientific  importance, 


376  INTERNATIONAL  ASTRONOMICAL  UNION 

thus:  P\  =  Trojan  Group,  p2  —  Hecuba  Group,  etc.;  v  for  variable, 
/  for  libration,  e  for  eccentricity,  i  for  inclination,  etc.  The  magnitude 
at  unit  distance  might  also  be  given.  An  investigator  could  thus  pick 
out  at  a  glance  the  asteroids  of  particular  interest  in  his  line  of  research. 

After  each  asteroid  has  been  properly  classified  and  designated,  cards 
should  be  completed  in  order  of  importance.  This  work  should  all  be 
done  under  the  auspices  of  the  International  Committee,  provided  such 
a  committee  adopts  some  plan  as  outlined  here. 

Ephemerides. — An  international  convention  will  have  to  be  held  for 
providing  observations  and  preliminar}'  orbit  determinations  for  newly 
discovered  planets  and  for  carrying  forward  the  computations.  It  would 
seem  wise  at  this  time  for  the  international  committee  to  canvas  the  differ- 
ent countries  as  to  the  share  of  burden  each  can  undertake.  At  the  out- 
set probably  different  countries  in  the  Union  would  care  for  the  asteroids 
discovered  in  their  own  country,  without  attempting  a  complete  duplica- 
tion of  the  work  now  in  progress  at  Berlin.  In  this  connection,  the  names 
of  the  observatories  and  astronomers  who  have  undertaken  to  secure  the 
necessary  and  sufficient  obser^^ations  in  the  case  of  each  planet  and  to 
carry  forward  the  computation  should  be  published. 

It  is  very  essential  that  an  understanding  be  reached  to  secure  the 
necessary  and  sufficient  observations  of  a  newly  discovered  object  to 
secure  a  satisfactory  orbit  sufficient  to  locate  the  body  of  the  next  oppo- 
sition and  to  avoid  all  unnecessary  observations  and  computations. 

After  the  International  Committee  has  adopted  definite  plans  in  re- 
gard to  the  foregoing  points  national  observatories  and  almanac  offices 
will  no  doubt  be  in  a  position  to  care  for  such  ephemerides  as  involve 
routine  computation  only.  The  whole  work,  however,  should  be  organized 
under  the  auspices  of  the  International  Committee. 

As  there  may  be  differences  of  opinion  no  definite  plans  are  proposed 
until  the  different  countries  are  able  to  state  what  assistance  they  can 
render. 

It  is  desired  that  monographs  be  published  for  the  benefit  of  various 
groups  of  research  men  by  persons  invited  to  undertake  this  task  by  the 
committee,  or  by  volunteers. 

Recommendations. — In  particular,  the  Committee  makes  the  following 
recommendations : 

1.  That  the  Executive  Board  of  the  National  Research  Council  be 
requested  to  secure  funds  for  the  preparation  of  a  history  and  bibliography 
of  comets  and  asteroids,  with  the  understanding  that  this  work  will  be 
undertaken  by  the  United  States. 

2.  That  the  International  Astronomical  Union  appoint  an  International 
Committee  on  Comets  and  Asteroids. 

3.  That  the  American  Delegation  to  the  International  Astronomical 
Union  submit  to  the  International  Committee  the  proposals  of  the  Amer- 
ican Committee  on  Comets  and  Asteroids  for  their  approval. 


INTERNATIONAL  ASTRONOMICAL   UNION  377 

4.  That  in  particular  a  preliminarv'  distribution  of  the  necessary  ob- 
servational and  computational  activities  among  the  countries  represented 
in  the  Union  be  agreed  upon,  on  the  basis  of  such  offers  as  may  be  received 
from  the  different  countries. 

5.  That  the  American  Delegation  pledge  that  it  will  arrange  for  the 
care  of  the  observ-ational  and  computational  work  incident  to  comets  and 
asteroids  discovered  in  the  United  States. 

A.  O.  Leuschner,  Chairman,  E.  W.  Brown,  G.  H.  Peters. 

APPENDIX  A 
MEMORANDUM    ON    CLASSIFICATION    OF   PLANETS 

Class  a.- — Asteroids  for  which  accurate  definitive  orbits  and  general 
perturbations  are  available. 

1.  Ordinary   asteroids   which   have   no   immediate   scientific   interest. 

Obser\'ations  of  these  should  be  suspended,  but  approximate 
ephemerides  should  be  provided  for  identification  purposes,  if 
accidentally  observ^ed. 

2.  Important  asteroids  of  further  scientific  interest  should  be  observ^ed 

in  accordance  with  prearranged  codperative  plans  with  the  object 
of  securing  sufficient  observations  for  the  scientific  purposes  in 
hand,  and  avoiding  unnecessary  multiplication  of  observ^ations. 
Ephemerides  should  be  published,  the  accuracy  of  the  ephemer- 
ides in  each  case  to  depend  on  the  research  requirements  for  that 
case. 
Class  h. — Asteroids  for  which  accurate  definitive  elements  are  available, 
but  no  general  perturbations. 

1.  Ordinary  asteroids.     Same  as  a  (1).     Approximate  general  perturba- 

tions should  be  computed  as  a  later  part  of  an  asteroid  program, 
as  opportunity  presents  itself,  preferably  only  the  principal  terms 
in  groups. 

2.  Important    asteroids.     Observations    to    be    dispensed    with    until 

general  perturbations  have  been  computed,  degree  of  accuracy 
to   depend   on   particular   scientific  requirements   in   each   case, 
then  same  as  a  (2). 
Class  c. — Asteroids  for  which  satisfactory  elements  are  not  available, 
but  which  have  been  sufficiently  obser\^ed  for  the  determination  of  satis- 
factory osculating  elements. 

1.     Ordinary  asteroids.     Same  as   a   (1).     Elements   to  be   improved, 
then  the  same  as  b  (1). 
Asteroids  for  which  osculating  elements  should  he  derived,  with  the 
use  of  special  perturbations,  accuracy  in  each  case  to  depend  on 
the  special  research  requirements;  then  same  as  h  (2),  then  a  (2). 

Class  d. — Asteroids  for  which  sufficient  observations  are  not  available 
for  satisfactory  orbit  determinations.     These  should  be  observ-ed  accord- 


378  INTERNATIONAL  ASTRONOMICAL  UNION 

ing  to  cooperative  plan  to  secure  necessary  and  sufficient  observations  to 
bring  them  through  the  preceding  classes  into  a  (1)  or  a  (2). 

Class  e. — Lost  asteroids.  These  should  be  made  the  object  of  special 
orbit  investigations  to  ascertain  range  of  solution,  and  most  probable 
orbit. 

Class  /. — New  discoveries.  A  fairly  definite  observational  programme 
for  necessar\^  and  sufficient  observations  during  discovery  opposition 
should  be  agreed  upon,  the  discoverer  to  be  responsible  for  the  execution  of 
the  observational  programme  in  cooperation  with  one  or  two  other  observa- 
tories, the  orbit  determinations  to  proceed  hand  in  hand  with  the  observa- 
tions, so  that  a  fairly  accurate  orbit  may  be  available  at  end  of  discovery 
opposition  to  serve  for  incorporation  of  asteroid  in  one  of  the  preceding 
classes. 

Accidental  discoveries  to  be  reported  to  central  agency  or  agencies  for 
assignment  of  observational  programme  and  orbit  computations. 

Particularly  interesting  cases,  such  as  1911  MT,  or  object  Wolf  1918, 
etc.,  to  be  generally  distributed  by  telegraph  to  stimulate  observation  and 
investigation. 

Class  g. — Asteroids  observed  insufficiently  even  for  preliminary  orbit 
determinations. 

SUPPLEMENTARY     RECOMMENDATIOXS     OF      COMMITTEE     OK     COMETS     AND 

ASTEROIDS 

Recommended  for  Reference  to  International  Committee  on  Comets  and 

Asteroids 

1 .  That  mean  places  of  asteroids  and  comets  visually  observed  with  an 
equatorial  be  published  instead  of  apparent  places.  At  present  the  orbit 
computer  makes  no  essential  use  of  the  apparent  place  reduction  of  the 
comparison  star.  It  is  practically  universal  to  employ  the  mean  place, 
corrected  or  uncorrected  for  annual  aberration  according  to  method,  ob- 
tained by  forming  apparent  place  of  object  minus  apparent  place  reduc- 
tion of  comparison  star.  This  mean  place  may  also  be  obtained  by  ap- 
plying Aa  and  A5  directly  to  mean  place  of  comparison  star.  In  case  the 
orbit  computer  wishes  to  take  account  of  the  differential  apparent  place 
reduction,  he  would,  if  apparent  place  were  discontinued,  be  limited  to  the 
use  of  the  differential  formulae,  which,  however,  are  not  longer  than  a 
single  apparent  place  reduction.  Thus  it  is  seen  that  the  proposed  change 
ivould  give  the  orbit  computer  directly  what  he  uses;  would  in  no  way  in- 
crease his  labor;  would  save  the  observer  an  apparent  place  reduction  for 
every  observation;  and  visual  observations  would  be  presented  in  the 
same  way  that  photographic  now  are. 

2.  That  each  observatory  adopt  its  own  distinctive  provisional  designa- 
tion for  asteroids  not  identified  up  to  the  moment  of  publication  with  a 
previously  discovered  one.     Washington  has  chosen  W  and  Johannesburg 


INTERNATIONAL  ASTRONOMICAL   UNION  379 

has  chosen  T,  followed  by  a  number,  but  it  might  be  anything  distinctive. 
It  is  advisable  that  this  always  be  preceded  with  the  year  of  discover}^ 
thus,  1917  Wlo,  1912  716,  etc.  This  will  enable  an  asteroid  to  be  re- 
ferred to  by  a  distinctive  designation  in  current  discussion  and  in  indexes, 
thus  facilitating  such  discussion  and  the  looking  up  of  references. 

3.  That  this  provisional  designation  of  asteroids  should  be  retained 
until  undoubted  identification  with  an  old  asteroid  or  until  identified 
at  a  second  opposition,  when  it  may  be  given  the  permanent  number 
designation.  This  would  prevent  holes  in  the  consecutive  numbering 
such  as  (132)  Aethra,  etc. 

4.  That  the  term  "astrographic,"  as  first  used  in  Greenwich  Observa- 
tions 1910,  be  more  generally  adopted  to  denote  the  position  of  an  object 
obtained  from  a  photographic  plate,  by  using  in  the  reduction  the  mean 
places  of  comparison  stars  at  the  beginning  of  the  3^ear.  Neglecting  the 
difi'erential  apparent  place  reduction,  it  is  identical  with  the  position  ob- 
tained by  applying  Aa  and  A5  directly  to  the  mean  place  of  the  comparison 
star,  as  mentioned  in  (1). 

5.  That  observers  be  urged  to  publish  observ-ation  times  in  decimal  of 
day,  G.  M.  T.  (Greenwich  Civil  Time  after  1925,  if  the  present  agitation 
results  in  discontinuance  of  astronomical  mean  time).  For  this  G.  M.  T. 
decimal  of  day  is  the  form  which  most  computers  use,  since  it  is  most 
convenient,  because  the  national  ephemerides  use  G.  M.  T. 

6.  That  the  ephemerides  give  the  rectangular  solar  coordinates  at  the 
beginning  of  the  year,  since  they  are  most  made  use  of  by  orbit  computers 
who  almost  universally  use  mean  place  at  beginning  of  year,  and  also  to 
give  these  coordinates  in  the  usual  manner  so  that  they  may  be  readily 
differenced.  The  Berliner  Jahrbuch  has  done  this  since  1868.  The  re- 
duction to  some  other  epoch  such  as  1900  or  1925  would  also  be  useful. 
In  addition  to  the  coordinates  the  velocities  of  the  coordinates  per  one- 
tenth  of  a  day  should  also  be  given  to  facilitate  interpolation  and  orbit 
computation  by  Laplacean  methods. 

7.  That  1900.0  be  adopted  for  the  publication  of  positions  of  asteroids 
and  for  orbit  computation.  Many  times  more  reference  stars  for  both 
photographic  and  visual  purposes  will  be  referred  to  1900.0  when  the 
astrographic  program  is  completed  than  to  any  other  equinox.  Perhaps 
more  photographic  positions  of  asteroids  are  now  published  than  visual 
and  probably  in  a  few  years  they  will  greatly  outnumber  the  visual.  Since 
it  is  easier  for  the  photographic  observer  to  derive  positions  in  the  equinox 
of  the  catalog,  it  would  seem  that  in  the  long  run,  more  computation 
will  be  saved  by  this  cooperation  of  observer  and  computer  than  by  the 
adoption  of  any  other  equinox  or  equinoxes. 

A.  O.  Leuschner,  Chairman,  E.  W.  Brown,  G.  H.  Peters. 


38o 


INTERNATIONAL  ASTRONOMICAL   UNION 


REPORT  OF  THE  COMMITTEE  ON  STELLAR  PARALLAXES 
At  the  present  time  determinations  of  stellar  parallax  by  the  trigono- 
metric method  form  part  of  the  regular  work  at  the  following  observatories; 


Allegheny 

Dearborn 

Greenwich .... 
IMcCormick. . . 
Mount  Wilson. 
Swarthmore . . . 
Yerkes 


APERTURE 

CHARACTER 

FOCAL  LENGTH 

30  inches 

Photographic  Refractor 

46  ft. 

18.5 

Visual  Refractor 

28 

26 

Photographic  Refractor 

23 

26 

Visual  Refractor 

32 

60 

Reflector 

80 

24 

Visual  Refractor 

36 

40 

Visual  Refractor 

62 

At  these  seven  institutions  material  sufficient  for  the  determination  of 
three  hundred  parallaxes  is  obtained  each  year.  The  average  probable 
error  of  one  determination  is  under  .01".   . 

Determination  of  stellar  distances  by  the  spectroscopic  method  are 
being  carried  out  at  Mount  Wilson  with  the  60-inch  reflector.  When 
the  100-inch  telescope  is  in  regular  operation,  a  larger  part  of  the  time  of 
the  60-inch  telescope  will  probably  be  devoted  to  obtaining  spectrograms 
for  this  purpose,  so  that  we  may  expect  a  rapid  increase  in  our  knowledge 
from  this  source.  This  committee  recommends  that  other  institutions 
be  urged  to  undertake  this  w^ork,  their  programs  to  include  a  large  number 
of  objects  already  obser\^ed  by  the  spectroscopic  method.  Attention  is 
called  to  the  fact  that  existing  spectrograms  (obtained,  for  example,  in 
radial  velocity  investigations)  could  profitably  be  examined  from  the  point 
of  view  of  absolute  magnitudes  and  stellar  distances,  at  least  for  the  spec- 
tral types  Fo  to  M. 

The  paucity  of  reliable  parallaxes  determined  by  the  trigonometric 
method  has  hitherto  been  a  serious  obstacle  to  the  effective  application 
of  the  spectroscopic  method,  since  the  latter  depends  principally  upon  the 
trigonometric  results  for  the  determination  of  relationships  between  line 
intensities  and  absolute  magnitudes  for  the  various  spectral  types.  The 
war  has  delayed  the  publication  of  much  material  that  will  overcome  this 
obstacle  to  a  considerable  extent,  and  it  is  likely  that  in  a  few  years  ample 
material  of  this  kind  will  be  at  hand.  One  of  the  most  important  services 
that  observers  employing  the  trigonometric  method  can  render  at  the 
present  time  is  to  arrange  their  programmes  with  the  needs  of  the  spectro- 
scopic method  in  mind. 

This  committee  makes  the  following  recommendations  in  addition  to 
those  already  mentioned : 

1.  That  observers  employing  either  method  should  record  the  reason 
for  each  star  being  placed  upon  their  observing  lists,  in  order  that  their 
results  may  be  properly  used  in  statistical  discussions. 


INTERNATIONAL  ASTRONOMICAL  UNION  381 

2.  That  they  should  aim  to  observe  a  large  number  of  stars  in  duplicate 
in  order  that  data  may  be  forthcoming  for  the  determination  of  systematic 
differences  and  systematic  errors. 

3.  That  a  catalogue  of  stellar  distances  in  brief  form  be  published  in 
the  near  future. 

4.  Most  important  of  all,  that  steps  be  taken  at  once  to  determine 
stellar  distances  by  both  trigonometric  and  spectroscopic  methods  in  the 
southern  hemisphere.  In  no  respect  is  our  knowledge  of  southern  stars 
as  meagre  as  in  this. 

Finally,  it  is  recommended  that  the  International  Astronomical  Union 
appoint  a  committee  to  promote  cooperation  along  the  lines  indicated. 
Frank  Schlesinger,  Chairman,  W.  S.  Adams,  S.  A.  Mitchell. 

REPORT  OF  THE  COMMITTEE  ON  STELLAR  PHOTOMETRY 

The  following  observations  and  suggestions  are  submitted  for  the  con- 
sideration of  the  American  delegates  to  the  meeting  of  the  International 
Astronomical  Union,  with  the  hope  that  they  may  be  helpful  in  the  or- 
ganization of  an  International  Committee  on  Stellar  Photometry.  It  is 
for  this  purpose  that  they  are  presented,  rather  than  as  a  program  for  the 
operations  of  such  a  committee  when  once  formed. 

The  organization  of  an  International  Committee  on  Stellar  Photometry, 
which  we  herewith  recommend,  requires  an  immediate  specification  of  the 
functions  to  be  exercised.  These  we  believe  may  be  summarized  as 
follows : 

(1)  To  advise  in  the  matter  of  notation,  nomenclature,  definitions, 
conventions,  etc.,  whose  universal  adoption  will  simplify  and  unify  the 
publication  and  use  of  photometric  results. 

(2)  To  plan  and  execute  investigations  requiring  the  cooperation  of 
several  observers  or  institutions.  The  necessity  for  cooperation  in  such 
investigations  may  arise  from  geographical  considerations,  from  the  magni- 
tude of  the  undertaking  or  from  the  demands  for  precision  which  can  be 
satisfied  only  by  combining  the  results  obtained  with  different  instruments 
and  under  widely  different  conditions. 

Thus  the  systematic  observation  of  variable  stars  requires  operations 
in  both  northern  and  southern  hemispheres  and  in  different  longitudes; 
again,  such  an  undertaking  as  the  reduction  of  the  provisional  magnitudes 
of  the  Carte  du  del  to  the  normal  scale,  because  of  the  labor  involved  if 
for  no  other  reason,  could  not  be  carried  out  by  any  single  institution; 
and,  finally,  the  peculiar  difficulties  and  numerous  sources  of  error  involved 
in  the  establishment  of  reliable  standards  of  brightness  raises  an  impera- 
tive demand  for  confirmation  which  can  be  satisfied  only  by  concerted  and 
cooperative  effort. 

The  nature  of  the  activities  included  under  (1)  is  sufficiently  obvious 
from  the  above  formulation.     There  can  be  no  question  as  to  the  desira- 


382  INTERNATIONAL  ASTRONOMICAL  UNION 

bility  of  a  central  committee  charged  with  decisions  relating  to  notation, 
nomenclature,  etc.  For  example,  in  the  matter  of  naming  newly  dis- 
covered variable  stars,  endless  confusion  can  be  avoided  only  through  the 
action  of  a  centralized  body  of  recognized  authority  and  responsibility. 
Nevertheless  some  elaboration  of  statement  is  necessary  in  order  to  em- 
phasize what  we  believe  to  be  a  sound  basis  of  procedure. 

A  sharp  distinction  should  be  drawn  between  the  adoption,  on  the  one 
hand,  of  definitions  and  conventions,  and,  on  the  other,  of  the  numerical 
results  which  flow  from  the  introduction  and  usage  of  such  definitions  and 
conventions.  The  adoption  of  a  definition  or  convention  naturally  should 
never  be  undertaken  hastily  or  without  detailed  consideration  of  all  the 
attendant  circumstances;  but  once  an  appropriate  formulation  has  been 
attained,  there  need  be  no  hesitation  or  objection  to  its  imiversal  acceptance. 
Thus  we  find  ever^-where  in  use  the  definition  of  the  scale  of  magnitudes 
represented  by  the  formula 

in    -  nio  =    -0.4  (log/  -  log/o). 

Similarly,  the  convention  adopted  by  the  committee  on  magnitudes  of  the 
Carte  du  del  relative  to  the  zero  point  of  the  photographic  scale  of  mag- 
nitudes finds  ready  acceptance  on  the  part  of  all  observers.  Or  again,  the 
definition  of  color-index  as  the  difference:  photographic  magnitude 
minus  visual  or  photovisual  magnitude,  affords  so  convenient  and  useful 
a  measure  of  the  color  of  a  star  that  it  meets  with  the  approval  of  every- 
one engaged  with  the  problems  of  stellar  photometr}^  Thus  we  find 
introduced  into  astronomical  practice  a  uniformity  and  standardization 
which  is  only  useful  and  helpful. 

The  practical  application  of  these  definitions  and  conventions  requires, 
however,  the  usage  of  numerical  standards  and  constants.  And  here 
caution  must  be  exercised  if  progress  is  really  to  be  aided.  A  definition 
or  convention  in  the  nature  of  the  case  possesses  elements  of  permanence 
and  invariability ;  but  a  numerical  constant  is  a  thing  of  the  day  to  be  dis- 
carded the  moment  a  more  precise  determination  becomes  available.  The 
quality  of  inconstancy,  the  ever-increasing  precision  which  characterizes 
the  metrical  results  of  science,  should  always  be  borne  in  mind;  otherwise 
there  is  danger  that  the  seal  of  authority  may  be  placed  upon  results  in 
which  authority  should  have  no  place.  The  thing  to  be  emphasized  is 
evidence,  not  authority,  and  the  evidence  should  be  frequently  reviewed. 

Thus  in  the  matter  of  magnitudes:  it  will  be  necessary  in  undertaking 
any  cooperative  investigation  to  specify  the  standards  which  are  to  be  used. 
The  selection  naturally  will  be  made  by  the  International  Committee 
after  a  critical  examination  of  the  evidence  underlying  the  results  then 
available;  but  it  should  be  clearly  understood  that  the  standards  thus 
chosen  are  for  that  particular  investigation  and  are  not  necessarily  to  be 
used  for  any  other  which  subsequently  may  be  undertaken.     In  the  present 


INTERNATIONAL  ASTRONOMICAL   UNION  383 

state  of  the  question  it  seems  undesirable  that  any  particular  set  of  stand- 
ard magnitudes  be  designated  by  the  adjective  "international."  Such 
an  action  on  the  part  of  an  International  Committee  would  necessarily 
convey  the  impression  of  an  authoritativeness  and  finality  of  decision  which 
it  would  be  difficult  to  justify  in  view  of  the  present  outstanding  differences 
in  the  results  of  different  observers. 

This  does  not  mean  that  there  should  be  no  international  standards. 
On  the  contrary,  standards  to  which  this  designation  may  properly  be  ap- 
plied should  be  established.  But  this  can  be  attained  only  through  a 
cooperative  effort  of  the  type  specified  under  (2).  The  question  wull  be 
reverted  to  later.  An  additional  remark  should  be  made  here,  however, 
as  a  supplement  to  the  above  considerations,  namely,  that  the  provisional 
character  even  of  any  act  of  "international"  standards  should  be  empha- 
sized, say,  through  some  such  designation  as  I.  C.  P.  1920  (International 
Committee  on  Photometry,  Standards  of  1920). 

We  believe,  too,  that  much  conserA^atism  should  be  displayed  in  the 
matter  of  standardization  of  methods  and  equipment.  As  an  illustration, 
it  is  well  known  that  photometric  results  obtained  by  visual  methods  de- 
pend upon  the  color  perception  of  the  eye  of  the  observer.  Thus  for  the 
Har\'ard  durchmusterung  {Harvard  Annals  45)  and  the  durchmusterung 
of  Muller  and  Kempf  (Potsdam  Pub.  9),  both  catalogues  of  visual  magni- 
tudes, Schwarzschild  finds  (Gottingen  Aktinometrie  B  16) 

H  -  P  =  -0.27  -  0.04(P  -  6.5)  +  0.23  {G  -  P) 

in  which  G"  —  P  is  the  color-index  obtained  by  comparing  Gottingen  photo- 
graphic with  Potsdam  visual  magnitudes.  The  last  term  of  the  equation 
represents  the  differences  which  are  to  be  attributed  to  peculiarities  of  color- 
perception.  In  visual  photometry  naturally  there  can  be  no  standardiza- 
tion in  the  sense  in  which  the  term  is  used  here.  Each  observer  must 
work  with  the  eye  with  which  he  has  been  provided. 

Of  late  5^ears,  however,  photovisual  magnitudes  have  been  much  used 
as  a  substitute  for  those  derived  visually.  An  isochromatic  plate  exposed 
behind  a  suitably  chosen  yellow  filter  affords  results  which  are  at  least 
approximately  the  same  as  those  obtained  visually.  But  photovisual 
magnitudes  are  obviously  dependent  upon  the  color-sensibility  of  the  par- 
ticular kind  of  plate  and  filter  employed,  and  in  this  connection  it  is  fre- 
quently suggested  that  a  standard  plate  and  filter  be  universally  adopted 
and  used  for  all  photovisual  observations. 

Unfortunately  the  difficulties  are  not  so  easily  to  be  avoided.  The 
suggestion  overlooks  a  third  contributing  factor  whose  significance  is  not 
generally  appreciated,  namely,  the  telescope.  The  selective  absorption 
by  the  glass  of  the  objective  or  by  the  silvered  surface  of  the  reflector 
plays  a  very  important  part  in  determining  the  color-sensibility  of  the 
equipment.     Moreover,  it  is  not  merely  a  question  of  refractors  as  against 


384  INTERNATIONAL  ASTRONOMICAL  UNION 

reflectors,  for  dififerent  objectives  seldom  behave  exactly  the  same  and 
not  infrequently  very  large  differences  are  to  be  met  with.  This  is  best 
illustrated  by  the  following  comparisons  of  different  series  of  photographic 
results.  Here  the  complicating  influence  of  a  filter  does  not  enter,  because 
no  filter  has  been  used,  and  the  effect  of  the  kind  of  plate  is  largely  elim- 
inated, because  with  some  exceptions  the  same  brand  of  plate  has  been 
used  throughout.  The  comparisons  show  only  the  term  depending  on  the 
color-index  C. 

MW— Greenwich  =  -f0.27C  \  .^^    ,^,.,         ^     ,     ^^      ^- 

- -^,     ^  .        ,  ,  .  '       „-_      Mt.   Wilson   Cont.    No.   97,   p.   28 

MW — Dziewulski  =  — 0 .  06C  J 

MW— 16-in.  Metcalf  =  +0.33C  1 

MW—8-in.  Draper  =  +0.06C      ,.^   „,.,        r>     .   ^t     no 

o  •      T-v  n %;  •      u        -7-  „   ,„„      Mt.  Wilson  Cont.  No.  98,  p.  t. 

8-in.  Draper — 0.5  in.  Ross-Zeiss  =  — 0.13C  j 

8-in.  Draper— 4-in.  Cooke  =  -f-0.21C  J 

Other  examples  might  have  been  added,  but  those  given  illustrate  the 
magnitude  of  the  eiTect  and  show  the  impracticability  of  restricting  the 
photographic  measurement  of  stellar  brightness  to  any  closely  specified 
region  of  the  spectrum,  for  the  observer  must  use  the  telescope  which  is 
available. 

Emphasis  should,  therefore,  be  directed,  not  toward  standardization, 
but  toward  the  publication  of  results  in  such  a  form  that  they  may  be  re- 
duced to  any  system  for  purposes  of  comparison  and  combination  with 
other  results.  Apparently  this  is  to  be  accomplished  only  by  giving  the 
color  of  a  star  in  addition  to  its  brightness.  Spectral  type  cannot  be  re- 
garded as  a  satisfactory  substitute  for  color,  for  it  is  now  known  that  the 
color-indices  of  stars  of  the  same  type-color,  especially  the  G's  and  /\ 's — 
may  differ  by  half  a  magnitude  or  more. 

Admitting  the  impracticability  of  basing  the  observations  upon  any 
prescribed  system  of  color  (in  the  sense  that  the  measurements  are  to  be 
made  within  certain  specified  limits  of  wave-length),  one  might  still  ask 
if  it  is  not  desirable  that  the  results  be  reduced  to  a  standard  system  in 
advance  of  publication,  in  order  that  all  catalogue  values  may  be  directly 
comparable.  The  answer  here  is  that  in  the  present  state  of  photometry 
the  reduction  factors  for  color  will  necessarily  be  uncertain,  and  hence 
subject  to  correction.  It  thus  appears  important  that  the  results  referred 
to  the  color  system  of  the  equipment  used  should  always  be  included  in 
the  published  results,  even  when  reduced  values  are  also  given. 

These  details  are  presented  as  an  indication  that  reservation  and  caution 
must  characterize  the  decisions  of  a  central  committee  in  case  its  activities 
are  to  be  helpful;  at  the  same  time  they  reveal  the  disconcerting  fact  that 
measures  of  stellar  brightness  will  attain  their  full  value  only  when  results 
for  the  colors  of  the  individual  stars  become  available.  This  is  strikingly 
shown  by  an  attempt  to  compare  the  results  of  the  Durchmusterung  of 
the  Selected  Areas  recently  issued  as  Harvard  Annals  101  with  photographic 


INTERNATIONAL  ASTRONOMICAL   UNION  385 

magnitudes  for  these  same  regions  determined  at  Mount  Wilson.  The 
color-sensibiUty  of  the  two  instruments — the  IG-inch  Metcalf  and  the  60- 
inch  reflector — is  so  different  that  the  comparison  is  meaningless  except 
for  the  few  stars  whose  colors  are  known.  The  differences  in  this  instance 
are  extreme,  because  of  the  exceptional  behavior  of  the  16-inch  Metcalf 
instrument.  A  similar  situation  must  be  met  in  comparing  the  magnitudes 
of  the  Polar  Sequence  determined  at  Greenwich  with  those  of  other  investi- 
gators. The  influence  of  the  instrument  is  here  also  unusually  large; 
nevertheless  such  differences  always  appear,  to  some  extent  at  least,  and, 
unless  taken  into  account,  vitiate  the  comparison  of  results  with  different 
instruments.  This  fact  was  recognized  by  Miss  Leavitt  in  her  investiga- 
tion of  the  Polar  Sequence  and  allowed  for  wherever  possible.  The  re- 
sulting color  system  in  Harvard  Circular  170  is  not  very  different  from  that 
of  the  Mount  Wilson  photographic  magnitudes;  but  the  true  relation  of 
the  results  of  these  two  investigations  can  be  determined  only  by  allowing 
for  the  difference  in  the  two  systems.  Owing  to  the  systematic  difference 
in  the  color  of  bright  stars  and  faint  stars,  there  is  a  direct  influence  upon 
the  scales,  whose  accumulated  effect  between  the  6th  and  10th  magnitudes 
amounts  to  nearly  a  tenth  of  a  magnitude. 

Before  leaving  these  general  considerations,  and  more  or  less  as  a  sum- 
mary of  them,  it  may  finally  be  remarked  that  in  our  opinion  the  most 
effective  cooperation  is  to  be  attained  by  granting  to  the  individual  in- 
vestigator the  greatest  freedom  of  initiative  and  operation  consistent  with 
the  ends  to  be  accomplished.  What  is  desirable  as  an  end  can  profitably 
be  determined  by  consultation  and  mutual  agreement;  but  a  healthful 
development  of  research  requires  that  the  individual  be  responsible  for  the 
means  by  which  its. objects  are  to  be  attained. 

The  organization  of  an  International  Committee  will  require  a  classifica- 
tion of  the  activities  which  it  is  to  undertake  and  the  appointment  of  various 
subcommittees.  These  naturally  will  find  their  origin  in  the  questions 
which  the  committee  must  consider,  hence  it  seems  desirable  that  a  few 
of  the  most  important  of  these  problems  should  be  passed  in  review. 

1.  Standards  oj  magnitude.- — With  proper  allowance  for  differences  in 
color  systems  and  zero  points,  the  photographic  scales  of  Harvard,  Green- 
wich (Chapman  and  Melotte),  Potsdam  (Dziewulski),  and  Mount  Wilson 
are  in  satisfactory  agreement  between  the  10th  and  16th  magnitudes.  The 
interval  including  the  brighter  stars  is  fully  covered  only  by  the  results 
of  Harvard  and  Mount  Wilson.  Here  there  is  a  scale  divergence  of  6%. 
For  the  reconcihation  of  this  difference  further  investigations  will  be  re- 
quired, which,  in  part  at  least,  should  be  in  the  hands  of  other  observers. 
The  question  is,  therefore,  very  definitely  one  for  the  consideration  of  an 
international  committee.  The  observations  should  preferably  be  made 
■on  the  stars  of  the  Polar  Sequence.  In  any  event  groups  such  as  the 
Pleiades  which  contain  no  red  stars  that  are  bright  should  be  avoided,  owing 


386  INTERXATIOXAL  ASTRONOMICAL   UNION 

to  the  fact  that  the  gradual  increase  in  color  with  increasing  magnitude 
makes  it  difficult  to  distinguish  the  influence  of  the  color  equation  of  the 
instrument  from  that  of  an  error  in  the  scale. 

The  visual  and  photovisual  standards  now  available  also  require  further 
attention.  These  will  most  conveniently  be  considered  in  connection  with 
the  photographic  standards. 

When  once  it  is  clear  that  all  serious  systematic  errors  have  been  elim- 
inated, the  committee  may  with  propriety  consider  the  combination  of  the 
results  of  the  different  investigations  for  the  formation  of  series  of  inter- 
national standards,  which  doubtless  would  then  require  revision  only  at 
infrequent  intervals. 

It  would  be  a  convenience  to  observers  if  the  adopted  values  were  re- 
ferred to  alternative  systems  of  color:  in  the  case  of  photographic  magni- 
tudes, for  example,  to  the  color  s^^stem  of  an  average  objective,  say,  that 
of  the  8-inch  Draper  telescope  which  is  essentially  that  of  the  Harvard 
Polar  Sequence,  and  also  to  the  color  system  of  the  reflector,  which  very 
likely  is  constant  or  nearly  so  for  all  instruments  of  this  type.  The  visual 
standards  should  be  referred  to  the  color  system  of  the  Harvard  Photom- 
etry; but  photovisual  standards  based  on  the  reflector  should  also  be  avail- 
able. The  standardization  of  a  plate  and  filter  for  use  with  the  reflector 
may  not  prove  feasible;  but  having  chosen  an  isochromatic  plate  which 
is  easily  obtainable  it  doubtless  would  not  prove  too  difficult  to  construct 
a  filter  such  that  the  combination  reproduces  the  adopted  standards.  Be- 
cause of  its  bearing  upon  various  physical  questions  such  as  stellar  tem- 
peratures, the  spectral  intensity-curves  corresponding  to  the  color-system 
used  should  in  all  cases  be  published. 

2.  Reduction  of  the  magnitudes  of  the  Carte  du  CielJ.o  the  normal  scale. — 
This  undertaking  has  been  in  the  hands  of  the  Committee  on  Magnitudes 
of  the  Carte  du  Ciel.  In  case  the  work  of  this  committee  is  merged  with 
that  of  the  organization  under  discussion,  the  investigation  will  immediately 
become  one  of  the  most  important  and  pressing  questions  before  the  newly 
organized  committee. 

Two  methods  of  procedure  are  possible:  (a)  Await  the  results  of  (1) 
above,  and  then  use  the  resulting  standards;  (6)  establish  the  scale  for  the 
Astrographic  Zones  with  the  aid  of  the  valuable  counts  recently  published 
by  Turner.  This  would  require  a  knowledge  of  the  star-density  as  a  func- 
tion of  galactic  latitude  and  longitude  for  each  interval  of  magnitude. 
Each  of  these  methods  has  its  advantages  and  disadvantages  which  will 
require  the  attention  of  the  committee. 

3.  Nomenclature  of  neu'ly  discovered  variable  stars. — Hitherto  in  the 
hands  of  the  Astronomische  Gesellschaft.  An  important  question  of 
policy  must  be  faced  in  this  connection.  Probably  the  Argelander  nota- 
tion should  be  continued,  because  of  its  convenience.  For  catalogue 
purposes,  however,  the  Harvard  notation  has  important  advantages,  be- 


INTERNATIONAL  ASTRONOMICAL   UNION  387 

cause  of  its  elasticity.     The  number  once  assigned  is  permanent  and  always 
places  the  star  in  its  proper  serial  order  in  the  catalogue. 

4.  Ephemerides  of  variable  stars. — Hitherto  published  annually  in  the 
Vierteljahrsschrift.  Again  a  question  of  policy  must  be  considered.  In 
case  this  very  desirable  aid  to  the  observer  is  to  be  prepared  under  the 
direction  of  the  International  Committee,  the  form  of  publication  should 
be  most  carefully  considered. 

5.  Catalogue  of  variable  stars. — Intimately  related  to  (3)  and  (4). 
A  complete  catalogue,  of  carefully  considered  form,  should  be  published; 
at  intervals  which  may  be  determined  by  experience  it  should  be  com- 
pletely revised.  In  the  interim  annual  supplements  containing  revisions 
and  additions  should  be  available. 

6.  Systematic  observation  of  variable  stars. — To  insure  a  proper  distri- 
bution of  effort  and  to  avoid  a  needless  duplication  of  results,  there  should 
be  mutual  agreement  between  observers  as  to  the  objects  to  be  observed 
or  at  least  an  announcement  as  to  objects  under  observation.  A  central 
committee,  as  a  clearing  house  for  the  dissemination  of  information  and  the 
arrangement  of  details,  would  prove  invaluable.  Directive  action  on  the 
part  of  the  committee  should  be  reduced  to  a  minimum.  The  affiliation 
of  associations  of  amateurs  should  be  invited. 

Other  questions  might  easily  be  added,  but  these  we  believe  sufficient, 
to  indicate  the  character  of  the  organization  required. 

Very  respectfully  submitted, 
F.  H.  Shares,  Chairman,  S.  I.  Bailey,  F.  C.  Jordan,  J.  A.  Parkhurst, 

Joel  Stebbins. 

REPORT  OF  THE  COMMITTEE  ON  DOUBLE  STARS 

I.  classification 
The  term  "double  star"  is  still  loosely  used  to  describe  any  pair  of  stars 
which  have  been  connected  by  micrometric  measures.  It  seems  desirable 
to  agree,  if  possible,  upon  some  more  exact  definition  and  to  adopt  some 
system  of  classification  and  of  printing  conventions  which  will  enable  us 
to  distinguish  between  pairs  of  difterent  character.  To  be  of  service, 
such  a  system  must  be  adopted  by  common  consent  of  astronomers  and 
such  consent  can  best  be  obtained  by  discussion  and  agreement  at  a  meet- 
ing of  the  character  of  the  proposed  International  Astronomical  Union. 
As  a  basis  for  discussion,  the  Committee  on  Double  Stars  suggests: 

1.  That  in  measuring  and  cataloging  nevi'  pairs  definite  limits  as  to 
magnitude  and  angular  separation  be  observed,  such  as  those,  for  example, 
proposed  in  The  Working  Definition  of  a  Double  Star,  published  in  A.  N. 
188,  1911,  (281). 

2.  That  double  stars  already  cataloged  be  divided  into  four  classes, 
as  follows;^ 

'  The  section  requested  the  committee  to  devise  a  different  mode  of  printing. 


388  INTERNATIONAL  ASTRONOMICAL  UNION 

Class  A. — Systems  for  which  the  measures  show  a  definite  curvature  of 
the  relative  path,  or  a  well-determined  variation  in  velocity  along  the  rela- 
tive path.  Class  A  systems  are  to  be  indicated  in  catalogs  by  the  use  of 
small  capitals;  e.g.,  61  cygni,  2  483,  8  EQUULEi. 

Class  B. — Systems  which  do  not  come  in  Class  A,  but  whose  physical 
connection  is  probable,  as  sho\vn  by  the  fact  that  the  components  have 
the  same  proper  motion.  Since  limits  must  be  adopted  to  exclude  stars 
belonging  simply  to  a  great  cluster  (e.g.,  Ursa  Major)  it  is  suggested  that 
pairs  be  entered  in  Class  B  only  if  the  angular  separation  is  less  than  100 
times  the  annual  proper  motion.  Pairs  under  1".0  separation  which  have 
been  under  observation,  say,  for  a  decade  or  more,  and  have  shown  no 
relative  motion  may  be  included  in  this  class  on  the  assumption  that  they 
are  moving  together  at  a  rate  less  than  ".01  per  annum.  Systems  of  Class 
B  are  to  be  indicated  in  catalogs  by  the  use  of  bold  faced  type;  e.g., 
2  110,  OS  175,02  424. 

Class  C. — Systems  whose  components  have  from  the  measures  apparently 
different  proper  motions.  This  class  will  include  the  purely  optical  pairs 
and  also  pairs  which  may  later  require  transfer  to  Class  A.  In  catalogs 
they  are  to  be  indicated  by  the  use  of  italics;  e.g.,  5  HercuUs,  2  2760, 
1:742. 

Class  D. — Systems  about  whose  motions  nothing  is  known.  This 
class  might  be  made  to  include  the  wide,  faint  pairs  apparently  simply  of 
historic  interest  as  well  as  new  pairs  of  unknown  proper  or  relative  motion. 
It  is  evident  that  pairs  entered  in  this  class  will  ultimately  be  transferred 
to  one  of  the  three  preceding  classes  or  dropped  entirely  from  our  catalogs. 
They  will  be  indicated  in  catalogs  by  the  use  of  lower  case  Roman  type; 
e.g.,  h  528,  A  3000. 

II.      COOPERATION 

It  is  highly  desirable  that  double  star  observers  work  in  closer  coopera- 
tion than  heretofore  to  insure  (1)  the  sufficient  observation  of  all  double 
stars  in  need  of  measurement  at  any  given  epoch;  and  (2)  the  avoidance  of 
unnecessary  duplication  of  measures.  Of  course  no  action  should  be  taken 
that  would  in  any  way  discourage  personal  initiative  in  the  choice  of  prob- 
lems or  methods;  but  it  is  suggested  that  certain  astronomers  who  have 
been  specially  interested  in  collecting  all  measures  of  double  stars  (e.g., 
Messrs.  Eric  Doolittle,  Robert  Jonckheere,  R.  T.  A.  Innes)  might  be 
asked  to  act  as  a  "clearing  committee,"  which  would  supply  any  observer 
wishing  it  with  a  list  of  double  stars  in  need  of  measurement  and,  in  prin- 
ciple, suited  to  the  power  of  the  telescope  to  be  employed. 

III.      GENERAL   CATALOGS 

Experience  in  using  and  handling  Burnham's  General  Catalog  has 
proved  the  inconvenience  of  having  the  data  for  any  one  system  recorded 


INTERNATIONAL  ASTRONOMICAL   UNION  389 

partly  in  one  volume  and  partly  in  another.  It  is,  therefore,  recommended 
that  in  future  catalogs  all  data  for  a  particular  system  be  printed  in  one 
place.  For  catalogs  printed  in  the  near  future  the  epoch  1950.0  is  recom- 
mended for  the  R.  A.  and  Decl. 

The  material  for  each  pair  should  include,  in  addition  to  measures  indi- 
cating the  character  of  the  motion,  the  magnitude  of  the  star  (combined 
brightness  of  the  components)  on  some  consistent  scale  (which  might  well 
be  that  adopted  in  the  photometric  magnitudes  of  the  Henry  Draper 
Catalogue),  the  spectrum  (when  known),  and  the  proper  motion  (in  polar 
coordinates,  not  in  R.  A.  and  Decl.).  For  systems  having  known  orbits 
all  the  elements,  and  not  simply  the  period,  should  be  recorded.  It  is 
not  at  all  essential  that  all  measures  should  be  recorded,  but  references 
should  be  given  to  all  published  measures,  orbits  and  notes.  This,  es- 
sentially, is  Professor  Doolittle's  plan  for  the  extension  of  Burnham's 
General  Catalog. 

The  ideal  catalog  would  cover  the  entire  sky.  If  this  ideal  cannot  be 
attained,  it  is  recommended  that  those  who  plan  the  publication  of  partial 
catalogs  come  to  an  agreement  as  to  limiting  declination  so  that  unnecessary 
overlapping  may  be  avoided. 

IV.      WORK    IN   THE    SOUTHERN    HEMISPHERE 

The  mos<"  important  piece  of  observational  double  star  work  that  can 
be  undertaken  at  the  present  time  is  the  extension  to  the  South  Pole  of  a 
survey  of  stars  to  about  the  9th  magnitude  along  lines  similar  to  those  of 
the  survey  of  the  northern  sky  completed  at  the  Lick  Observatory,  and  the 
systematic  remeasurement  of  all  the  closer  pairs  in  the  southern  sky 
which  have  already  been  cataloged.  A  careful  examination  of  all  pub- 
lished data  indicates  that  at  least  1800  double  stars  with  angular  separation 
under  b"  remain  to  be  discovered  among  the  stars  as  bright  as  9.0  magni- 
tude in  the  southern  half  of  the  sky — two  thirds  of  them  in  the  area  south 
of  -30°  declination.  This  assumes  the  southern  sky  to  be  as  rich  in  such 
systems  as  the  northern.  Further,  there  is  only  one  system  (a  Centauri) 
south  of  —  40  °  for  which  we  have  satisfactory  orbit  elements ;  there  are  at 
least  18  such  north  of  +40°. 

At  present  the  only  workers  in  this  field  are  Mr.  Innes,  at  Johannes- 
burg, using  a  9-inch  refracting  telescope,  and  Mr.  Dawson,  at  La  Plata, 
using  a  17-inch  refractor.  A  larger  telescope  in  a  favorable  position  is 
urgently  needed.  Using  a  telescope  of  20  to  25  inches  aperture  in  a  good 
location,  a  competent  observer  could  extend  to  the  South  Pole  such  a 
survey  as  has  been  mentioned  in  about  six  years  and  could  at  the  same  time 
secure  measures  of  all  close  known  pairs  south  of  -30°  declination.  Any 
action  that  can  be  taken  by  the  International  Astronomical  Union  to  en- 
courage and  assist  such  an  undertaking  either  through  one  of  the  observa- 
tories already  existing  in  the  southern  hemisphere  or  through  a  special  ex- 
pedition from  the  north  is  heartily  to  be  recommended. 


390  INTERNATIONAL  ASTRONOMICAL  UNION 

V.      COMMITTEE    ON    DOUBLE    STARS 

Finally,  your  Committee  recommends  the  appointment  of  an  inter- 
national committee  on  double  stars  to  act  under  the  authority  of  the  In- 
ternational Astronomical  Union. 

Robert  G.  Aitken,  Chairman,  Eric  DoolittlE,  W.  J.  Hussey. 

Note. — As  the  committee's  work  was  carried  on  by  correspondence 
there  was  not  time  for  a  complete  discussion  in  advance  of  the  meeting 
of  the  Section.     The  following  comments  were  added  by  Mr.  Hussey: 

"1.  Personally  I  do  not  attach  very  much  importance  to  the  formal 
definition  of  a  double  star.  I  am  inclined  to  accept  our  heritage  from  the 
past  and  work  according  to  our  best  judgment  for  the  future.  The  at- 
tempts made  to  define  a  double  star  in  terms  of  magnitude  and  distance 
have  generally  broken  down  by  not  being  sufficiently  inclusive,  owing  to 
the  movements  of  the  stars  themselves. 

"2.  It  does  not  seem  to  me  wise  to  complicate  the  printing  of  results 
by  the  use  of  different  kinds  of  type  for  the  different  classes  of  double 
stars,  such  as  capitals,  small  capitals,  italics,  lower  case,  and  bold  face, 
etc.  Such  attempts  lead  to  unsightly  printed  pages,  and  to  the  necessity 
of  keeping  constantly  in  mind  the  nomenclature  used.  In  my  opinion 
it  is  better  to  follow  the  prevailing  practice  of  using  brief  descriptive  terms, 
which  carry  their  own  meaning,  such  as  binary,  optical,  pair,  fixed,  etc. 

"3.  The  visual  double  stars  are  evidently  binaries  or  optical  pairs. 
To  which  class  a  given  star  belongs  can  only  be  ascertained  from  a  suffi- 
ciently extended  series  of  micrometrical  measures,  and  such  a  series  may 
require  many  years.  Until  such  measures  are  obtained  the  status  of  a 
pair  remains  undetermined.  It  is  not  justifiable,  as  is  proposed  in  the 
section  "Class  B"  of  the  Report,  to  regard  all  pairs  whose  distances  are 
under  r'.OO  as  having  common  proper  motions  when  no  change  is  shown 
by  measurements  extending  over  so  brief  a  period  as  ten  years.  Longer 
series  of  measurements  may  show  some  such  stars  to  be  optical  pairs, 
others  binaries,  and  still  others  common  proper  motion  pairs. 

"4.  Pairs  whose  components  have  different  proper  motions  are  optical 
systems.  No  star  of  this  class  can  be  a  binary,  and,  therefore,  appropriate 
to  be  put  in  Class  A,  as  suggested  in  the  paragraph  headed  Class  C  of  the 
report. 

"o.  Northern  Work.  At  the  present  time  the  most  pressing  need  in 
the  north  is  the  remeasurement  of  the  pairs  discovered  during  the  past 
twenty  years,  and  especially  the  close  pairs  discovered  at  the  Lick  Ob- 
servatory. 

"6.  Southern  Work.  In  the  south  there  is  needed  the  measurement 
of  the  known  pairs,  not  recently  measured,  and  the  examination  under 
good  conditions  of  the  southern  stars  to  the  ninth  magnitude  for  the  dis- 
covery of  new  pairs. 


INTERNATIONAL  ASTRONOMICAL   UNION  391 

"In  this  connection  it  may  be  stated  that  the  Observatory  of  the  Uni- 
versity of  Michigan  began  some  years  ago  the  construction  of  a  24-inch 
refracting  telescope  for  double-star  work  in  the  Southern  Hemisphere. 
The  mounting  for  this  instrument  was  nearly  completed  five  and  a  half 
years  ago,  when  work  upon  it  had  gone  as  far  as  was  practicable  until  the 
objective  could  be  obtained.  As  soon  as  the  glass  for  the  objective  can 
be  obtained  this  instrument  will  be  completed,  and  then  taken  to  the 
Southern  Hemisphere  for  double-star  work  and  for  other  observations. 
No  site  has  been  definitely  selected  for  this  instrument.  It  will  be  taken 
to  that  place  which  promises  the  best  results. 

W.  J.   HUSSEY." 

REPORT  OF  THE  COMMITTEE  ON  STELLAR  CLASSIFICATION 

Your  Committee  recommends  the  following  proposal  for  adoption  by 
the  American  Section,  and  presentation  by  its  delegation  at  the  interna- 
tional meeting  at  Brussels. 

CLASSIFICATION   OF   SPECTRA 

(a)  That  the  methods  of  determining  the  spectral  class,  according  to 
the  Draper  Classification,  which  have  been  developed  by  Adams  and 
Kohlschiitter,  be  adopted  as  an  extension  of  the  international  standard  of 
classification. 

(6)  That  the  notation  of  the  Henry  Draper  Catalogue  (Harvard 
Annals,  vol.  91)  be  adopted  in  the  case  of  stars  of  Classes  R  and  N. 

(c)  That  the  notation  of  the  Henry  Draper  Catalogue  be  adopted  for 
the  spectra  of  gaseous  nebulae,  and  that  P50  be  employed  to  denote  spec- 
tra intermediate  between  gaseous  nebulae  and  fifth-type  stars. 

(d)  That  a  series  of  standard  stars  be  chosen,  representing  typical 
spectra,  separated  by  not  more  than  five  divisions  of  the  Draper  scale 
(such  as  BO,  B5,  AO,  etc.)  and  that  reproductions  of  negatives  of  these 
spectra  be  published  for  the  benefit  of  astronomers  generally. 

(e)  That  the  presence  of  the  more  noteworthy  spectral  peculiarities 
(such  as  bright  lines,  unusually  sharp  or  diffuse  lines,  and  the  peculiarities 
in  intensity  associated  with  bright  or  faint  absolute  magnitude,  and  with 
the  Cepheid  type  of  variation)  be  denoted  by  distinctives  ymbols  appended 
to  the  ordinary  designation  of  the  spectral  class. 

(/)  That  a  Committee  on  Stellar  Classification  be  appointed  by  the 
International  Astronomical  Union,  which  shall  undertake  the  preparation 
of  the  list  and  reproductions  of  standard  spectra  (recommendation  (d)) 
and  the  formulation  of  the  notation  for  spectral  peculiarities  (recommenda- 
tion (e))  after  consultation  with  the  most  experienced  investigators  in 
this  field. 

In  explanation  of  (e)  it  may  be  noted  that  the  use  of  new  distinctive 
symbols  for  spectral  peculiarities  is  proposed  because  the  small  Roman 


392  INTERNATIONAL  ASTRONOMICAL   UNION 

letters  at  present  employed  to  denote  certain  characteristics  are  not  used 
in  the  same  sense  in  different  spectral  classes. 

The  remaining  recommendations  explain  themselves,  and  all  the  recom- 
mendations have  received  the  unanimous  approval  of  the  members  of  the 
Committee,  either  during  preliminary  discussion,  or  in  their  final  form. 
H  N.  Russell,  Chairman,  W.  S.  Adams,  A.  J.  Cannon,  R.  H.  Curtiss. 

REPORT  OF  THE  COMMITTEE  ON  RADIAL  VELOCITIES 

We  beg  to  recommend  to  the  American  Section  of  the  International 
Astronomical  Union: 

1.  The  formation  of  a  Committee  on  Radial  Velocities,  in  the  Interna- 
tional Astronomical  Union,  whose  duty  it  shall  be  to  encourage  and  pro- 
mote research  in  this  field. 

2.  There  should  be  cooperation  among  radial  velocity  observers  to 
the  ends  that  duplication  may  be  limited  to  necessary  and  desirable  de- 
grees, that  the  resources  of  the  various  observatories  may  be  applied  chiefly 
to  those  problems  for  which  they  are  the  more  uniquely  adapted,  and  that 
the  accumulation  of  accurate  and  homogeneous  results  may  be  expedited. 
It  is  not  proposed  that  the  individuality  of  investigators,  as  to  selection 
of  problems  and  methods,  be  interfered  with,  even  by  suggestion,  but  only 
that  the  evident  advantages  of  cooperation  be  available  to  all  qualified 
observers  who  seek  them. 

3.  A  Committee  of  the  American  Astronomical  Society,  embracing 
the  leading  radial  velocity  observers,  or  their  representatives,  in  1910-11 
gave  careful  consideration  to  the  proposal  that  radial  velocity  determina- 
tions should  be  extended  to  several  thousand  stars  in  the  Harvard  Re- 
vised Photometry  fainter  than  those  previously  observed  for  this  purpose, 
on  the  basis  of  cooperative  division  of  effort.  All  of  the  members  but  one 
were  of  the  opinion  that,  however  strongly  they  might  desire  to  engage 
in  the  suggested  cooperative  plan,  their  telescopic  resources  were  too  weak 
to  give  promise  of  coping  successfully  with  many  additional  stars.  In 
the  meantime  a  60-inch  and  a  73 -inch  reflecting  telescope  have  engaged 
heavily  in  this  work,  and  other  great  reflectors  are  under  construction  or 
nearing  completion.  We  are  of  the  opinion  that  cooperation  is  now  prac- 
ticable and  desirable.  We  recommend  that  those  institutions  engaged 
extensively  in  measuring  the  radial  velocities  of  stars  should  endeavor  so 
to  coordinate  their  programs  that  the  work  of  determining  the  radial  ve- 
locities of  the  stars  in  Boss's  Preliminary  General  Catalogue  shall  be 
divided  amongst  them  on  the  basis  of  their  latitudes,  the  light  gathering 
powers  of  their  telescopes,  etc. 

4.  The  present  situation  in  the  Southern  Hemisphere  closely  resembles 
that  in  the  Northern  Hemisphere  in  the  year  1910.  The  intensive  use 
of  very  large  reflecting  telescopes  in  the  Northern  Hemisphere  will  soon 
leave  radial  velocity  determinations  in  the  southern  sky  far  behind,  and 


INTERNATIONAL  ASTRONOMICAL  UNION  393 

thus  create  a  lack  of  symmetry  and  balance  in  the  results  for  the  two  hemi- 
spheres which  will  impose  regrettable  limitations  upon  their  statistical 
power.  This  will  be  unfortunate.  There  is  immediate  and  serious  need 
for  increased  observing  resources  in  the  Southern  Hemisphere,  based  upon 
the  use  of  reflecting  telescopes  60  inches  and  greater  in  diameter.  Organiza- 
tion for  this  service  should  be  encouraged.  It  is  mutually  understood  that 
the  Victoria,  Lick,  and  Mt.  Wilson  observatories  are  prepared  to  form  their 
radial  velocity  programs  in  this  manner. 

5.  Observers  equipped  with  medium-sized  telescopes  should  not  hold 
back  from  radial  velocity  work  because  telescopes  of  much  greater  power 
are  engaged  extensively  in  this  field.  They  should  not  be  misled  into  assum- 
ing that  the  relative  exposure  times  vary  inversely  as  the  areas  of  the  ob- 
jectives of  the  telescopes;  under  average  atmospheric  conditions  the  ex- 
posures are  more  nearly  as  the  inverse  diameters  of  the  objectives.  The 
instruments  of  medium  power  may  find  much  useful  work  to  do  in  observ- 
ing the  brighter  stars  of  Classes  O,  B  and  A,  whose  spectra  contain  few  and 
broadened  lines,  with  reduced  dispersion ;  and  many  such  stars  are  waiting 
observation. 

6.  The  investigation  of  spectroscopic  binaries  is  a  field  in  which  more 
workers  may  find  fruitful  employment.  This  is  especially  true  of  the  south- 
ern sky.  There  is  need  for  the  application  of  reflecting  telescopes  to  fur- 
ther study  of  spectroscopic  binary  stars  in  whose  spectra  the  K  line  of 
calcium  varies  but  slightly  in  wave-length.  There  are,  of  course,  many 
other  minor  problems  to  which  radial  velocity  methods  could  be  applied 
with  promise  or  certainty  of  valuable  results. 

7.  Consideration  should  be  given  to  questions  of  wave-lengths  and 
methods,  to  insure  that  results  obtained  at  all  observatories  be  homoge- 
neous, comparable  and  reducible  to  one  system.  This  principle  should  apply 
not  only  to  bright  stars  of  a  given  spectral  class,  but  to  bright  and  faint 
stars  of  the  same  class  as  observed  with  spectrographs  of  widely  different 
dispersions,  and  as  far  as  possible  to  stars  of  all  the  different  spectral 
classes. 

8.  There  exist  at  various  observatories  a  great  number  of  spectro- 
grams obtained  primarily  for  radial  velocity  determinations.  We  recom- 
mend that  these  spectrograms  be  utilized  for  estimates  of  the  absolute 
magnitudes  of  the  corresponding  stars,  and  therefrom  the  spectroscopic 
parallaxes  of  these  stars. 

W.  W.  Campbell,  Chairman,  Walter  S.  Adams,  J.  S.  Plaskett. 

REPORT  OF  THE  COMMITTEE  ON  REFORM  OF  THE  CALENDAR 

I 
At  this  very  unsettled  time  in  the  world's  history  all  sorts  of  reformers, 
wise  and  otherwise,  are  springing  up  advocating  changes  in  all  sorts  of 


394  INTERNATIONAL  ASTRONOMICAL  UNION 

things.  It  is  advisable  that  scientific  organizations  of  standing  be  con- 
servative in  their  advocacy  of  far-reaching  reforms  touching  the  every-day 
Hfe  of  the  people,  at  the  present  moment,  even  though  such  reforms  seem  in 
themselves  desirable. 

II 

The  calendar  can  undoubtedly  be  revised  or  reformed  to  advantage. 
The  following  suggestions  for  such  revision  or  reform,  favored  by  your 
Committee,  are  presented  for  your  consideration  without  recofmnendation 
as  to  whether  action  to  accomplish  them  should  be  advocated  for  the  pres- 
ent year: 

1 .  The  year  of  twelve  months  to  be  divided  into  four  quarters  of  three 
months  each,  and  the  arrangements  for  the  first  quarter  to  repeat  them- 
selves precisely  in  each  of  the  other  quarters.  The  first  month  of  each 
quarter  to  have  thirty  days;  the  second  month  thirty  days;  and  the  third 
month  thirty-one  days.  This  accounts  for  ninety-one  days  in  each  quarter, 
or  364  days  in  all. 

The  remaining  day  in  ordinary  years  to  be  "New  Year's  Day."  It  is 
to  be  given  no  other  descriptive  title.  It  is  not  to  belong  to  any  week  nor 
to  any  month.  It  begins  the  year.  January  1  to  be  the  day  following 
New  Year's  Day. 

The  366th  day  of  a  leap  year  to  be  likewise  an  extra  day,  bearing  an 
appropriate  name  (perhaps  "Leap  Day"),  but  no  week-day  name,  nor 
should  it  be  a  part  of  any  month.  It  may  be  (a)  the  day  following  Decem- 
ber 31,  hence  the  day  preceding  New  Year's  Day,  or  {b)  the  day  follow- 
ing June  31,  or  (c)  the  day  following  Christmas  Day  (at  the  present  time 
the  day  following  Christmas  Day  is  a  holiday  in  some  countries).  It  is 
assumed  to  be  a  holiday — it  comes  only  one  year  in  four. 

January  1  to  fall  on  Monday.  From  this  it  results  that  the  first 
month  in  each  quarter  (January,  April,  July,  October)  begins  on  Monday 
in  every  year;  that  the  second  month  in  each  quarter  (February,  May, 
August,  November)  begins  always  on  Wednesday;  and  that  the  third  month 
in  each  quarter  (March,  June,  September,  December)  begins  always  on 
Friday.  Further  results  of  this  are  that  (a)  the  first  day  of  the  month 
never  falls  on  Sunday,  (6)  the  fifteenth  day  of  the  month  never  falls  on 
Sunday,  (c)  the  thirtieth  day  of  the  month  never  falls  on  Sunday,  (d)  the 
last  day  of  each  quarter  (the  31st  of  March,  June,  September,  December) 
always  falls  on  Sunday,  (e)  the  thirty-day  months  always  have  four  Sun- 
days each,  (/)  the  thirty-one-day  months  always  have  five  Sundays  each, 
(g)  the  number  of  week-days  in  the  month  is  twenty-six  for  every  month, 
(h)  holidays  always  fall  on  the  same  day  of  the  week.  This  proposed  cal- 
endar is  outlined  in  the  following  table,  which  will  serve  for  all  years  alike. 
Leap  day  is  assumed  to  follow  December  31. 


INTERNATIONAL  ASTRONOMICAL   UNION 


395 


New  Year's  Day 

First  Quarter 

January 

February 

March 

Second  Quarter 

April 

May 

June 

Third  Quarter 

July 

August 

September 

Fourth  Quarter 

October 

November 

December 

Leap  Day- 

Monday 

1 

8     15     22 

29 

6 

13     20 

27 

4 

11     18 

25 

Tuesday 

2 

9     16     23 

30 

7 

14     21 

28 

5 

12     19 

26 

Wednesday 

3 

10     17     24 

1 

8 

15     22 

29 

6 

13     20 

27 

Thursday 

4 

11     18     25 

2 

9 

16     23 

30 

7 

14     21 

28 

Friday 

5 

12     19     26 

3 

10 

17     24 

1 

8 

15     22 

29 

Saturday 

6 

13     20     27 

4 

11 

18     25 

2 

9 

16     23 

30 

Sunday 

7 

14     21     28 

5 

12 

19     26 

3 

10 

17     24 

31 

This  would  be  a  perpetual  calendar,  and  need  be  printed  but  once. 

If  this  calendar  should  be  adopted  it  should  go  into  effect  at  the  beginning 
of  a  year  which,  according  to  the  present  calendar,  would  begin  with 
Monday  in  order  to  avoid  such  confusion  as  might  arise  from  the  adding 
or  dropping  certain  days  of  the  beginning  week.  According  to  the  present 
calendar  the  next  year  that  begins  on  Monday  is  1923,  and  the  next  fol- 
lowing year  to  begin  on  Monday  is  1934. 

It  should  be  pointed  out  that  according  to  the  proposed  calendar  the 
Sun  will  come  to  the  Vernal  Equinox  about  March  19  or  20  instead  of 
March  21  or  22  as  under  the  present  calendar. 

2.  The  day  to  be  divided  into  twenty-four  hours  numbered  consecu- 
tively from  one  to  twenty-four,  the  noon  hour  to  be  twelve. 

3.  The  astronomical  day  to  begin  at  midnight. 

R.  T.  Crawford,  Chairman. 

Signed  after  expressing  very  strong  preference  for  "Leap  Day"  follow- 
ing December  31,  in  order  to  break  the  continuity  of  the  weeks  only  once 


per  annum. 


W.  W.  Campbell. 


Signed,  excepting  ii  2,  relating  to  the  24-hour  day,  because  it  would 
necessitate  an  impossible  change  of  dials  and  mechanisms  in  all  existing 
timepieces.  Harold  Jacoby. 

REPORT  OF  THE  COMMITTEE  ON  RESEARCH  SURVEYS 
One  of  the  objects  of  the  National  Research  Council,  as  expressed  in 
the  Executive  Order  issued  by  President  Wilson  on  May  11,  1918,  is 
"to  survey  the  larger  possibilities  of  science,  to  formulate  comprehensive 
projects  of  research,  and  to  develop  effective  means  of  utilizing  the  scientific 
and  technical  resources  of  the  country  for  dealing  with  these  projects." 
The  Research  Council  has  already  undertaken  the  preparation  of  re- 
search surveys,  pointing  out  important  possibilities  in  both  scientific 
and  industrial  research.     The  chief  objects  of  these  surveys  are: 

1.     To  aid  the  specialist  in  recognizing  the  wider  bearing  of  his  in- 


396  INTERNATIONAL  ASTRONOMICAL  UNION 

vestigations  and  the  importance  of  organizing  them  in  such  a  way  as  to 
render  his  efforts  most  productive. 

2.  To  indicate  the  possibiUty  of  applying  in  other  branches  of  science 
the  special  instruments,  methods,  or  results  developed  in  particular  fields. 

3.  To  formulate  large  and  important  research  projects,  calling  for 
special  financial  support  or  for  the  cooperation  of  investigators  in  the  same 
field  or  of  those  dealing  with  other  branches  of  science. 

4.  To  encourage  more  active  investigation  in  the  borderlands  between 
the  various  branches  of  science. 

The  first  of  the  research  surveys  relating  to  astronomy  was  written  in 
1917  by  Dr.  Henry  Norris  Russell,  but  withheld  from  publication  because 
of  the  war.  This  has  recently  been  revised,  and  will  shortly  appear  among 
the  Bulletins  of  the  National  Research  Council  under  the  title  "Some 
Problems  of  Sidereal  Astronomy."^  The  recent  report  of  Dr.  C.  G. 
Abbot,  entitled  "The  Larger  Opportunities  for  Research  on  the  Relations 
of  Solar  and  Terrestrial  Radiation,"^  is  also  well  adapted  for  publication 
as  a  Research  Council  Bulletin,  and  your  committee  recommends  that  it 
be  brought  out  in  this  series  in  the  near  future. 

We  also  recommend  that  Professor  E.  W.  Brown  be  requested  to  pre- 
pare for  publication  a  survey  of  the  gravitational  problems  of  the  solar 
system.  Later  Bulletins  should  deal  with  cosmogony,  the  atom  and  elec- 
tron in  sidereal  astronomy,  the  future  possibilities  of  research  in  stellar 
spectroscopy,  stellar  distances,  and  other  subjects.  A  synopsis  of  the  adap- 
tation of  physical  apparatus  to  astronomical  problems  would  also  be  a 
valuable  contribution,  especially  if  it  indicated  some  of  the  astronomical 
possibilities  of  recently  developed  physical  methods. 

Because  of  the  importance  of  obtaining  the  personal  views  of  leading 
investigators  on  the  opportunities  for  research  in  their  respective  fields, 
it  is  not  proposed  that  any  single  branch  of  astronomy  be  exclusively  dealt 
with  by  a  single  writer.  The  suggestive  value  of  these  reports  is  likely 
to  be  greater  if  they  are  prepared  by  individuals  rather  than  by  committees, 
as  in  the  latter  case  the  average  view,  involving  the  consensus  of  opinion, 
is  substituted  for  the  special  view  of  men  who  have  approached  the  subject 
from  different  directions. 

Your  committee  requests  that  it  be  continued  and  authorized  to  ar- 
range for  the  preparation  and  publication  of  research  surveys  in  astronomy, 
in  conformity  with  any  general  plan  that  may  be  adopted  by  the  National 
and  International  Research  Councils. 

George  E.  Hale,  Chairman,  F.  R.  Moulton,  Harlow  ShaplEy. 

'  Reprint  and  Circular  Series  of  the  National  Research  Council,  Number  5. 
-  Reprint  and  Circular  Series  of  the  National  Research  Council,  Number  7. 


UC  SOUTHERN  REGIONAL  LISRAR 


D     000  584  798     3 

Bulletin  of  the  National  ResearchTIouncil 

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Number  4.  North  American  forest  research.  Compiled  by  the  Com- 
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(In  press.) 


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Council.  Presented  for  the  Committee  by  L.  H.  Baekeland,  Acting 
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